How to choose a locksmith (or any other local tradesperson)
If you're looking for a locksmith because you have locked yourself out (or you think you might), or you are changing or upgrading your locks, be careful who you choose.
There are two approaches to locksmithing: there is NDE (non-destructive entry) which is the use of techniques that open the lock without damaging it, like picking for example; and then there are the people armed with very few tools other than a drill.
I.e. there are those who want to get the door open as fast as possible and then probably sell you a new lock. (Check that the new lock is actually put in the door, and isn't just put on your bill!) …
… And there are locksmiths who take pride in only drilling as a last resort. And who, if they have drilled, do it neatly with a small hole that's easily repaired in a sound fashion.
One operative, sent by a national "locksmith" franchise, of the kind that have the half-page adverts in the phone books, drilled a 20 mm hole (that's nearly an inch!) through a door and lock! No genuine locksmith would ever need more than an 8mm hole, and, as mentioned earlier, even that is the last resort not the first.
Local or call centre
If you suspect that you are talking to a call centre rather than a locksmith or a locksmith business, my advice is to hang up and have another go at locating a local independent locksmith.
If you ring a national call centre, you have no control over who they send, you are going to pay more, often quite a lot more. You can, of course, still be unlucky with anyone you do business with, but by following a few simple checks, you stand more chance of a job decently done for a reasonable price when you choose a local locksmith.
And, of course, check the price (mine are here), minimum charge (mine is 1 hour), call-out fee (I don't charge a call-out) and from how are away they are coming (I am coming from SW4, London).
If you're reading this, it's highly likely that you will use Google or Bing to begin a search for services. Be reasonably specific in your search. A locksmith, for example, doesn't need to serve a million people to make a living, so while there might only be one or two locksmiths serving the high fells, there will be several dozen serving London. So you're not going to have much success with searching Google for "locksmith london"; you would be more successful with "locksmith wandsworth, "locksmith lambeth" or locksmith SW8", etc.
Now, the call centres know this, so they flood the web with fake, local-appearing web sites. (It only costs a few pounds a year to register and keep a domain name.) So you have to do one more thing. Check the web site for evidence that they really are local to you. Look at the contact details (or perhaps the home page) for the address, the phone number and the fax number. A fake, "local" web site will hide its address and phone number: you simply won't find a postal address and the phone number will be an free 0800 number, a local charge 084, etc. number; or the number might be a national-rate 087 number and, personally, I don't call people who try to make extra money from my phone call to them. It's entirely possible that a genuine web site is offering an 0800 or an 084, etc. number, in which case you need to look for the other evidence like the fax number: if you're in 020 and their fax is 01242, you can be fairly suspicious.
If you're really getting into all of this, try a search for a tradesperson, in an area that's 100,000 people distant from you. Here, that might be "locksmith crystal palace". You may see three of four sets of web pages that look almost exactly the same as some of those appearing in your local search. Those are probably the fakes.