Streatham Common Locksmith Service Team
Local locksmith team
15 Jul 2026 14 min read
Your front door has let you down — maybe someone tried to force it, maybe the key is turning stiffly, or maybe you have just moved into a flat on Streatham High Road and want to know exactly what the previous tenant could still open. The question almost every caller asks before anything else is the same: do I need the whole lock replaced, or just the cylinder? It is a genuinely important distinction, because these are different jobs with different scopes, and understanding which one applies to your situation means you can have an informed conversation with your locksmith before anyone turns up.
This guide walks through the two options clearly — what a cylinder is, what the lock case or mechanism is, when swapping the cylinder alone is the right call, and when the entire lock needs to come off the door. We cover uPVC and composite doors, traditional timber doors with Yale nightlatches or 5-lever mortice deadlocks, and the factors that affect what your job will involve. If you would rather just talk it through, our team is available around the clock — call 020 4530 9860 and we will tell you honestly what we think you need.
## Cylinder vs. Lock Case: What Each Part Actually Does
The cylinder is the barrel-shaped insert that your key slides into — it is the part that reads the key profile and, when the correct key is turned, releases the cam or tailpiece that operates the lock mechanism. On a uPVC or composite door, the euro cylinder is the entire active security component, sitting in the middle of the multipoint lock and held in place by a single retaining screw. On a timber door with a Yale-type nightlatch, the cylinder sits inside the nightlatch body. On a 5-lever mortice deadlock, the keyhole and levers do the same job, though the design is different. In all cases, the cylinder or keyway is what grants access — it is the component that is changed when we talk about changing who can open a door.
The lock case or mechanism is everything else: the body of the lock, the bolt or latch, the internal levers or gears, the multi-point hooks or rollers on a uPVC door, and the chassis fitted into or onto the door itself. This hardware does not care which key you use — it simply executes the movement the cylinder commands. When people ask how do you change a lock or how do you change a door lock, what they usually mean in UK terms is: can the cylinder alone be swapped so that old keys no longer work, without touching the rest of the mechanism? In most cases, yes — and that is usually the quicker, less disruptive job.
## When a Cylinder Swap Is All You Need — Lock Change London Made Simple
Changing just the cylinder makes sense in a clear set of scenarios. You have moved into a new property and want certainty that estate agent keys, builder's keys, or the previous occupant's copies are dead. A flatmate has moved out on bad terms. Your euro cylinder has been identified as a standard, non-anti-snap model and your insurer or letting agent has asked you to upgrade to a TS007 3-star rated cylinder — a sensible upgrade on any uPVC or composite door in Streatham, where cylinder snapping remains one of the most common forced-entry methods. In all of these cases, the multipoint lock mechanism itself is functioning correctly, the door aligns properly, and the hardware is in good condition. All that changes is the cylinder insert.
Measuring matters here. If you are sourcing a euro cylinder yourself before we arrive, you need to measure from the centre of the retaining screw hole to each end of the cylinder — for example, 35mm on the outside and 45mm on the inside gives you a 35/45 cylinder. Getting this wrong means the cylinder will either not reach the cam or will protrude and become a snapping target. For a 5-lever mortice deadlock, the question of how do you measure a backset on a mortise lock comes up: the backset is the distance from the edge of the door to the centre of the keyhole, and it determines which case size fits your door correctly. We always measure on-site before fitting anything, so you do not need to worry about getting this wrong — but it is useful context if you are trying to understand your own door.
## When the Whole Lock Must Be Replaced — Door Lock Replacement London
Sometimes the cylinder is fine but the mechanism behind it has failed or been compromised. The most common reasons we see this in Streatham homes — particularly in the Victorian and Edwardian terraces around Streatham Common and the period conversions near Streatham Hill station — are physical damage from a forced entry attempt, wear in the gearbox of a multipoint lock causing hooks or rollers to drop out of alignment, a broken latch or deadlock that no longer throws fully, or a nightlatch body that has been repeatedly forced until the internal springs have given up. In these situations, replacing the cylinder would leave you with a lock that still does not work properly, or one that cannot be secured at all.
uPVC door lock repair London calls often begin with a customer saying the key turns but the door will not lock, or the handle lifts but nothing engages. This almost always points to the gearbox inside the multipoint mechanism rather than the cylinder. Replacing a multipoint mechanism is a more involved job — the old unit is removed from the door edge, a compatible replacement is sourced (gearbox dimensions and hook positions vary between manufacturers), and the new mechanism is fitted, adjusted, and tested through the full range of positions. The cylinder from the old door can often be retained or transferred if it is a good-quality anti-snap model, which saves time and means your existing keys continue to work. We confirm exactly what is needed and give you a fixed price before any work begins — the final quote depends on the lock type, the parts required, and the time of day we are called out.
## Traditional Timber Doors, Mortice Deadlocks, and Combination Locks — What Changes and What Stays
On a traditional timber front door you will usually find two locks working together: a Yale-type nightlatch (spring latch, operated by a small oval cylinder) and a 5-lever mortice deadlock fitted below it. Insurers frequently specify that the mortice deadlock meets BS3621 — if yours does not, or if you are upgrading after a break-in attempt, the whole mortice case may need to come out and a compliant one fitted in its place, because the case body itself carries the BS3621 rating, not just the keyway. The nightlatch, by contrast, can usually be re-cylindered on its own if the body and backplate are undamaged.
Combination lock questions come up less often for home doors but do arise for internal storage, outbuildings, and secondary security. When someone asks how do you change the code on a door lock or how do you change a combination lock code, the answer varies entirely by lock model — some have a reset button accessed with the current code, others require a tool-reset procedure described in the manufacturer's instructions, and others cannot be reset by the user at all. If you have inherited a combination lock with an unknown code and are wondering how do you change a combination lock in that situation, the honest answer is: it depends on the lock design, and in many cases the lock will need to be replaced rather than reset. If you are unsure, call us and describe what you have — we will tell you straight away whether it is something we can sort on a visit.
One question we hear regularly is do you need to change the cylinder on a new lock when it comes direct from a builder or new-build developer. The short answer is yes, in almost every case. Builder's locks are frequently installed with standard master-key systems so that one site key opens every flat or house on the development during the build. Until that cylinder is replaced with one keyed uniquely to your door, the site master key — and potentially copies of it — can still operate your lock. This is a quick job on a euro cylinder door, and it is worth doing before you bring furniture in.
## Locked Out London? Here Is What to Do Before Calling — and When to Call Us
If you are locked out of your home in the Streatham area, the first sensible steps are the ones that do not involve the lock at all: check whether a trusted neighbour holds a spare key, try any other entrance you have legitimate access to such as a back gate or patio door, and contact your landlord or letting agent if you are a tenant, as they may hold a copy. These steps are worth trying not because a locksmith visit is anything to be concerned about, but because they can save you waiting time if a spare key is genuinely close by.
When those options are exhausted — or if you are standing on a cold Streatham pavement at midnight — call 020 4530 9860. We are a 24 hour locksmith London service operating every day of the year, including bank holidays, and we will send a locksmith straight away. We are usually with you in about 30 minutes, though travel time can vary depending on where in the Streatham area we are working at that moment. When you call, our team will ask a few quick questions to understand your door type and whether this is a lockout, a damaged lock, or a security upgrade — that way we arrive with the right parts and can give you an accurate price on the phone before we set off. As an emergency locksmith London, we work on all door types: uPVC, composite, timber, and communal entrance doors on blocks of flats.
One thing worth understanding: a lockout does not automatically mean a lock change. A skilled locksmith will open the door with the least disruptive method available for your specific lock and door type. If the lock and cylinder are undamaged and your keys are inside, the cylinder is often preserved entirely. It is only when the lock has been damaged — by a failed break-in attempt, a snapped cylinder, or wear — that replacement becomes necessary. We will always tell you clearly which applies before we do anything.
## 25 Services We Provide Across Streatham and the Surrounding Area
Our mobile locksmith team covers Streatham Common, Streatham Hill, Streatham Vale, Norbury, Thornton Heath, Balham, Tooting, Tulse Hill, West Norwood, Brixton, and surrounding SW and SE postcode districts. Here is a specific breakdown of what we handle: euro cylinder replacement on uPVC doors, euro cylinder replacement on composite doors, anti-snap cylinder upgrades to TS007 3-star rating, 5-lever mortice deadlock supply and fitting, BS3621-compliant mortice deadlock installation, Yale nightlatch cylinder swap, Yale nightlatch full unit replacement, multipoint lock gearbox replacement on uPVC doors, multipoint lock gearbox replacement on composite doors, multipoint lock hook and roller adjustment and repair, non-destructive door opening after lockout, timber door lock fitting and alignment, communal entrance door lock replacement, flat front door lock upgrade, door frame repair following attempted forced entry, cylinder measurement and sizing advice on-site, snap-resistant euro cylinder upgrade assessment, boarding-up service following break-in (temporary security), broken key extraction from cylinder, broken key extraction from mortice lock, lock lubrication and servicing, door alignment and adjustment affecting locking performance, uPVC door handle replacement where linked to lock function, nightlatch deadlocking mechanism check and repair, and security audit of all external door locks for landlords and tenants. All of these services are available 24 hours a day, seven days a week — call 020 4530 9860 to confirm availability and get a fixed price before we travel.
## Pricing, What Affects Your Quote, and How to Avoid Surprises
We do not publish fixed prices for cylinder or lock replacement work, because the honest answer is that the right quote depends on several factors that vary from door to door. The type of lock — a standard euro cylinder, a high-security TS007 cylinder, a BS3621 mortice case — affects parts cost significantly. The time of day matters: an evening or weekend call-out involves different logistics than a weekday job. Travel distance across the Streatham area and beyond affects how long our locksmith is off other work. And the condition of the existing door and frame can change the scope of the job once we are on-site. What we commit to is this: we tell you the full price on the phone before anyone travels to you. There are no surprise additions when we arrive, and there is no pressure to proceed if you decide not to go ahead once you have heard the figure. The call-out charge is included in what we quote — we explain everything clearly before we set off.
Frequently asked questions
How do you change the cylinder on a door lock in the UK — is it the same as replacing the cylinder?+
In the UK, changing the cylinder as it is understood in some other markets — where a locksmith reconfigures the existing pin stack inside the cylinder so that only a new key works — is not widely offered as a standard service. The common and practical equivalent is a cylinder replacement: the old euro cylinder or nightlatch cylinder is removed and a new one is fitted, with new keys cut to match. The lock body, door furniture, and mechanism all stay exactly as they are. So when people ask how do you change a lock in a British context, the answer is almost always: we swap the cylinder. It is a straightforward job on most uPVC and timber doors, and it immediately voids all previously issued keys.
Do you need to change the cylinder on a new lock when you move into a property?+
Yes, in almost every situation. When a property changes hands — whether through a sale, a new tenancy, or a new letting — the previous occupants may have had multiple copies of the key made over the years. Builder's keys on new-build developments often operate a master system covering multiple homes on the same site. Even if you are handed a single key on moving day, there is no way to know how many copies exist. Replacing the cylinder is the only way to be certain your locks respond only to keys you have issued yourself. It is a quick job, it does not involve touching the lock mechanism or the door, and it is good practice recommended by most home insurers.
How do you measure a backset on a mortise lock, and why does it matter when replacing a lock?+
The backset on a mortise lock is the horizontal distance measured from the edge of the door (the door stile) to the centre of the keyhole. You measure it with the door open, running a tape from the face edge of the door straight across to the middle of the keyhole opening. Common backset sizes on UK doors are 57mm and 44mm, though older or non-standard doors can vary. This measurement matters because a replacement mortice case must match the existing backset, otherwise the keyhole will not align with the escutcheon plate and the bolt throw may not clear the frame correctly. If you are unsure, do not guess — we measure on-site before sourcing any parts, so the replacement fits correctly first time.
My key turns but the uPVC door will not lock — is this a cylinder problem or the mechanism?+
This is almost always the multipoint lock mechanism rather than the cylinder. When the key turns freely but the hooks, rollers, or locking points do not engage, the gearbox inside the lock has usually worn or failed — a common issue on uPVC and composite doors that have been in daily use for several years, particularly in the winter when door frames expand slightly and put extra load on the mechanism. The cylinder itself is usually fine in this scenario and can often be carried over to the new mechanism. We handle uPVC door lock repair across Streatham and the surrounding area and can usually diagnose the fault quickly once we see the door. Call 020 4530 9860 — we are available 24 hours a day and can tell you on the phone what is likely involved before we arrive.
