The single most common residential job we do has nothing to do with a fault. You have just moved in, everything works, and you have no idea how many keys exist. Estate agents, previous tenants, cleaners, a builder from four years ago — the honest answer is that nobody knows, and the previous owner does not know either. A lock change on moving day is the cheapest security decision available to you, and it closes that question permanently.

On a typical London property this is quicker and less disruptive than people expect. On a uPVC or composite door we usually replace only the euro cylinder, not the whole mechanism, which keeps the cost sensible and takes minutes per door. On a timber door with a mortice lock the lock body itself is changed. Either way you end up with one new key that everybody in the household carries, and nothing in circulation that you did not hand out yourself.

It is worth doing every external door at the same time, including the back door and any side gate or garage access. We see a lot of homes where the front door has been upgraded and the back door is still on its original lock from the 1990s, which rather defeats the point — an intruder will always try the least visible door first. Where you have several doors, keying them alike so a single key operates all of them is usually a small additional cost and makes daily life considerably easier.

If you are renting rather than buying, check your tenancy agreement before changing anything and speak to your landlord — most are perfectly willing, and many will pay for it, but changing locks without permission can put you in breach and leave you liable for reinstatement at the end of the tenancy.

• Full lock change on moving day
• Euro cylinder swap on uPVC and composite doors
• Mortice lock replacement on timber doors
• Keyed-alike sets so one key opens every door
• Back doors, side gates and garages included
• Booked slots to suit completion day

Lock snapping is the reason most London homes need a cylinder upgrade, and it is worth understanding why it works. A standard euro cylinder has a weak point at its centre. Applied with leverage, that weak point fails, and the lock can be defeated in well under a minute with tools bought openly. It is quiet, quick, and leaves very little sign from the street, which is exactly why it became the dominant method.

The fix is a cylinder rated to resist it — TS007 3-star, or Sold Secure Diamond. These are engineered to sacrifice a section and leave the mechanism intact and locked when attacked. We fit these as standard on residential lock replacement work rather than treating them as an upsell, because a like-for-like replacement of a snapped cylinder simply resets the same vulnerability.

Length matters as much as rating. A cylinder that protrudes more than a couple of millimetres past the handle gives an attacker something to grip, and an over-long cylinder in a 3-star rating is far weaker than a correctly measured one in a lower grade. This is why we measure on site rather than fitting a standard size. It is also the most common fault we find on doors that have been "upgraded" by somebody else.

For timber doors the equivalent standard is BS3621, which covers five-lever mortice deadlocks. Most UK home insurance policies specify BS3621 on final exit doors, and a surprising number of households discover at claim time that what they have is a five-lever lock that was never certified. The kitemark is stamped on the faceplate — if you are unsure, we will check it while we are there and tell you either way.

• TS007 3-star anti-snap cylinders
• Sold Secure Diamond rated options
• Cylinders measured to your door, not guessed
• BS3621 five-lever mortice deadlocks
• Insurance compliance checked and confirmed
• Existing hardware assessed free while on site

If your door needs a lift, a shove, or a particular knack before the handle will go up, the multi-point mechanism is wearing out. That knack is not a quirk of the door — it is you compensating for a gearbox under strain, and gearboxes that are compensated for eventually seize completely, usually with the door locked shut.

The underlying cause is very often alignment rather than the mechanism itself. Doors settle. Hinges drop by a few millimetres over years of use, the hooks stop meeting their keeps squarely, and every single operation then puts load through parts never designed to take it. Replace the gearbox without correcting the alignment and the new one wears out the same way, just later. We check and adjust hinges and keeps as part of the repair, which is the difference between a fix and a postponement.

Patio doors and bi-folding doors have the same failure pattern with more moving parts and tighter tolerances, so alignment matters even more. Sliding patio doors additionally suffer from worn rollers, which make the door heavy and put strain on the locking point every time it is closed. Bi-folds have multiple leaves that must stay square to each other, and a single dropped hinge affects the whole run.

We carry the common gearboxes, keeps, handles and cylinders, so most door repairs are finished on the first visit. Where a mechanism is obsolete and needs ordering, we make the door secure and usable in the meantime rather than leaving you with a door that cannot be locked overnight. Composite doors deserve a specific mention, because they are heavy and the extra weight accelerates hinge drop considerably compared to a hollow uPVC slab. If you have a composite front door that is two or three years old and has started to bind at the top corner, that is the weight doing its work and it is worth adjusting before the gearbox starts taking the strain.

• Multi-point gearbox repair and replacement
• Hinge and keep realignment
• Sliding patio door rollers and locks
• Bi-folding door track and locking repair
• Handles, spindles and euro cylinders
• Common parts carried on the van

Not every lock problem is an emergency, and not every failing lock needs replacing. A key that is getting stiff often just needs the cylinder cleaning and correctly lubricating — and specifically not with the general-purpose oil most households reach for, which attracts dust and eventually gums the mechanism worse than before. A dry graphite or PTFE-based lubricant is what these mechanisms are designed for.

A door that has started catching on the frame is usually a hinge or a weather issue rather than a lock issue, and timber doors in particular move seasonally — a door that sticks every winter and frees up in spring is behaving normally and needs adjustment, not replacement. We would rather tell you that than sell you a lock you do not need, and we say so on site more often than people expect.

Rekeying is worth knowing about as an alternative to replacement. Where the lock body is sound, changing the pin configuration gives you a new key without new hardware. It is a sensible option after losing keys, after a relationship ends, after a lodger moves out, or when a set of keys goes missing at work and you cannot be sure where. It costs less than a full replacement and takes less time.

Where a lock genuinely has reached the end of its life, we will say so plainly and quote for the replacement then and there. Cylinders and mortice locks do wear out with normal use — roughly a decade of daily operation is typical, less on a busy family front door — and a mechanism that is dropping pins or turning roughly is telling you it has done its time.

• Stiff and sticking lock repairs
• Correct lubrication, not household oil
• Rekeying without replacing hardware
• Door adjustment for seasonal movement
• Honest assessment of what needs replacing
• Window locks and restrictors

Smart locks have moved well past the novelty stage, and the practical case for them in a London home is mostly about not handing out physical keys. A cleaner, a dog walker, a contractor doing a week of work, family visiting for a fortnight — each of those traditionally means cutting a key you may never get back. A smart lock lets you issue a code, set when it works, and remove it afterwards.

The most common question is what happens when the battery dies, and it is the right question to ask. Reputable smart locks warn you for weeks beforehand, and most retain a physical key override or external power contacts. We will not fit a lock that leaves you with no way in if the electronics fail, and on a final exit door we generally recommend keeping a mechanical override available.

Not every door suits every product. Door thickness, the existing cylinder type, whether the door is timber or uPVC, and how the multi-point mechanism engages all affect what can be fitted cleanly. Some retrofit units replace only the internal thumbturn and leave the external cylinder intact, which is neat and reversible; others need the full cylinder replaced. We assess the door before recommending anything rather than turning up with one product and making it fit.

It is worth being clear that a smart lock is a convenience upgrade first and a security upgrade second. The cylinder it is built around still needs to be anti-snap rated, because an intruder attacking your door is not going to attempt to hack the app — they are going to attack the same physical weak point they always have.

• Retrofit smart locks for existing doors
• Temporary codes for cleaners and contractors
• Entry logs and phone alerts
• Mechanical key override retained
• Door compatibility assessed first
• Anti-snap cylinder underneath as standard

Landlords and letting agents are among our most regular residential clients, largely because lock work between tenancies is predictable, repeatable and easy to get wrong. The key-control problem is the same one homeowners face on moving day, except it recurs with every changeover and the liability sits with you rather than the occupant.

The legal dimension matters in flats and shared houses. Any door on an escape route must open from the inside without a key — that means a thumbturn cylinder or a nightlatch with an internal release, not a keyed deadlock. It is a genuinely common finding in older converted properties, where a well-meaning previous landlord has fitted a mortice deadlock to a flat entrance door and inadvertently created a fire risk. We will flag it if we see it, and fit compliant hardware.

For portfolios we work through multiple addresses in a day, which is considerably cheaper per property than individual callouts and much easier to schedule around checkout dates. We can supply a written record of what was fitted at each address, which is useful for your own records and for demonstrating compliance if it is ever questioned.

Where a tenant is locked out mid-tenancy, we attend as an emergency callout and can bill the landlord, the agent or the tenant depending on how you would rather handle it — agreed in advance, so nobody is arguing about it on the doorstep at eleven at night. For blocks and converted houses we can also key communal entrance doors to a restricted profile, so that keys cannot be casually copied at a high street kiosk and every replacement has to come back through you. It costs slightly more per key and removes an entire category of problem, particularly in buildings with a long history of tenants and no record of how many communal keys were ever issued.

• Lock changes between tenancies
• HMO-compliant thumbturn escape locks
• Multiple properties attended in one day
• Written record of hardware fitted
• Tenant lockout attendance
• Billing arranged in advance