In Scotland if the local authority does provide any pest control services, the local Environmental Health office would be the first point of call. If they don't (for example Aberdeenshire don't) then EH should be able to point you to commercial organisations.
I'm actually surprised that you don't get mice in the house every year if you leave in the country and in a traditional build house, unless your cats have access to all the underfloor and roof spaces. We don't have cats, and get mice from early Autumn every year. Due to the amount of damage they do we use lethal force, spring traps set in all accessible spaces together with poison. I don't find it necessary to bait the traps.
What signs do you see or hear (or smell)? Mice will normally make chewing noises as well as the "pitter patter of tiny feet", droppings are quite recognisable and so is the smell, although Field Mice aren't quite as smelly has House Mice.
Reading this thread has reminded me to go round on what we call "mouse patrol", checking traps and making sure the bait stations are topped up. We rarely hear a mouse but the bait gets taken and the traps get one now and again.