My name is John Deacon. I am a chartered engineer (CEng) and a certified locksmith. I am a member of the Institute of Certified Locksmiths and I carry an identity card.
When dealing with lock-outs, I will always start with non-destructive entry (NDE) techniques. More than three-quarters of locks can be opened without drilling or damage.
If you are choosing a locksmith, ask about prices, ask about minimum charge, ask about callout fee, ask about when they will arrive and ask if they do "NDE"—using the abbreviation—don't actually say "non-destructive entry". If they say, "NDE? What's that then?", the chances are that they are drillers and not locksmiths.
I am a real person, really based in the Lambeth area in SW4. Why would I say that? Well there are national call centres who put up web sites purporting to be those of local locksmiths and of course are not. If you call them the chances are that you won't get a local locksmith; you might not even get a locksmith at all.
I can't offer 24-hour cover, but there are no set hours so it's always worth trying a call to us.