It’s very easy to panic and call the first number you see on Google, but please remember the first 3 or 4 adverts are sponsored and usually national companies that don’t have a locksmith in the area, but they might tell you they have and then phone round to find someone willing to attend at exorbitant price.
A local locksmith if they intend to stay in business for a long time will need to do a good job, look for any trade memberships, personally I use “The Buy With Confidence” scheme run by trading standards as my credibility and “Check a trade” for advertising and feedback.
It is important that the locksmith carries enough stock, it is not always possible to open a door without damaging the lock or there might be a number of locks that need to be changed at the same time as a matter of urgency. I carry enough different lock to always be able to leave a property secure, i also carry spare gearboxes for most of the common upvc door locking mechanisms, if you have a rare locking mechanism then I have temporary locks so again the property can always be left secure.
I have the ability to cut copy keys for most lock in my van so 9 out of 10 times I can complete the job on the first visit.