It depends entirely on the type of locks involved. The majority of residential homes in the US have semi-standardized lock bore and setback sizes so most anyth

It depends entirely on the type of locks involved. The majority of residential homes in the US have semi-standardized lock bore and setback sizes so most anything you pick up for dirt cheap at your local home improvement retailer will bolt right on. I'm not sure if there's the same level of standardization in the UK, but in most of Europe locks are of a design that allows you to replace the cylinder with a couple of screws from the inside. The locks themselves typically cost more but the labor is pretty much nonexistent. The only way you'd need to pay that much to have locks changed is if you're needing to do actual physical work on the door or jamb itself. Or if your locksmith is overcharging you because you don't know any better.