You might not get a Gas Safe certificate as it may be that they replaced the boiler, but not the valves on the radiators (you would only get a Gas Safe certificate if it was inspected straight away afterwards and was found to comply. I am pretty sure if a boiler has been installed in the last 2 or 3 years, the radiator valves must be switched to thermostatic ones or you will not comply fully with the regulations - someone correct me if I am wrong here but I am pretty sure I am right).
I would not let it affect my offer on the house too much. I would take out yearly plumbing/boiler/gas cover with someone like British Gas or Scottish Power. As part of their cover they typically provide an annual boiler service.
I have the cover. Have called them up on bank holiday Mondays in February at 10 at night when the boiler has packed in and there has been no cost (other then the monthly charge of course).
By the way, I don't work for any of the energy companies.

