Thanks for your quick responses.
Is there only one VIN plate on these cars?
Both the cars seem to have been well looked after, interiors very clean, and engine bays seem to be spotless too. The three door doesn't seem to have been thrashed, and the five door has been a London car for a while which is never really good (pot holes, humps, traffic etc), but obviously I can't really tell how they've been treated.
Also, the three door seemed to have very low coolant, although no discernable leaks in the engine / spots on the floor. Do you think this could have been due to the car not having been driven for the last couple of months?
Certainly the lack of service history book is a worry, but would evidence of service (ie garage receipts with registration printed) be an adequate substitute? Also, with regards to the 5-door, without having the old MOT certificates is there anyway to accurately verify the mileage?
I'm still a bit confused, and there's another very similar one that I may be looked at too...