I do not agree with that. I was in the process of buying a Robin Regent that had just come out of an Annual Inspection all signed off. I took my local engineer (a Robin expert) to view the aircraft and he found
i) That ADs were outstanding
ii) That the aircraft was not airworthy and had to ground it
iii) Parts of the wooden frame were severely damp and had to be replaced
The most important thing would have been to submit the documentary evidence of all this to the CAA.
They may not care (for this could lead to a shutdown of a fair bit of the UK maintenance business) but on the other hand they might.
The important thing for a pre-buy is to get a trusted individual (not a company) to have a look at it and provide an informal view. It's going to cost a few hundred quid at least, especially since so many planes rarely fly (or haven't flown for months or longer before finally selling) so that an engine borescope is essential.