Its a main dealer thing...over price a old car so they dont have to bother doing it. They earn more doing servicing work than repairs such as that. There's no need to remove the head either to trace where the fault lays...a simple cylinder leak-down test (not a compression check..and also not a fluid block test..different things) should identify whats failed imo. As said else where I think, it sounds like just a bent valve tbh and maybe a damaged valve guide as well. Ive been meaning to change the missuses 1.7 Pumas belt now for around a year...I think you've just pushed me into doing it at last