Well to a point yes. If they are going to re-shell it then the VIN numbers probably wont be stamped by the drivers seat. If the VIN is there then scratch it with a screwdriver, if they filled the original VIN number with filler and then stamped a new number in it will come off when you scratch it. Check for welds around this area too - to see if they welded in the old VIN number from the original shell.
Usual stuff applies - check alignment of panels, wear on steering wheel and gearknob. Ask *why* they are selling such a classic. Get the reg number up on here and RSOC and see if anybody knows the car. Give Derek - the RSOC registrar a ring and see if he knows the car.
The HPI report will tell you if it's ever been stolen and recorded or crashed and recorded. They are not infallible mind you.
The Bristol one certainly sounds good - 2 previous owners and looks pretty much unmolested under the bonnet - even the original airfilter/airbox is on it. They also have every MOT from new - a good sign, and some receipts/paperwork etc. It certainly sounds ok, but the proof will be when you see it - it may be a dog!