I had an AA one on my current car, as it was very cheap for its age, but with very high mileage and wanted to know if there was anything obvious major wrong with it. Wasn’t expecting to find out about everything, just the showstoppers as at the price I was paying I could live with niggles. Got a fairly clean bill of health – no idea how useful that was, but after 2.5 years (and it passing the last couple of MOTs with no work needed, after needing tyres and an exhaust patch on the first one) I’ve not discovered anything they missed.
Might have been a waste of money, but I was prepared to waste £100 on checking out a car which was £1000s cheaper than anything of a similar age I’d seen.