Getting three quotes is all very well - but what do you then do with them? Take the most expensive because that's most likely to be best quality? Take the lowest because that saves most money? Go for the middle one to get the best of both worlds? How do you judge whether any of the people who've quoted are actually any good?
This "get three quotes" advice has been around since Noah put the ark out to tender, but no one giving the advice ever follows up with what happens next. Maybe, once upon a time, when everyone was reliable, honest and truthful (before pigs forgot how to fly) you could get three quotes and confidently take the lowest.
You're going to allow this person into your home, probably trust him with a key to come and go, and let him - nay, ask him to - drill, chase out, bash about your property, then leave you with something that if it goes wrong could kill you.
Fine, get your three quotes. But decide for yourself which of the people concerned you'd feel happy with working for you in your home, possibly over an extended period. It's got to be someone you can get on with a feel you can trust. Then ask him for the phone number of his last customer and ring them up, ask if he did a good job for them - he'll pass you to someone he knows will give him a good reference, but it's worth a try.
Best of all, ask around friends. workmates, family, for a recommendation.
PJ