Bit of an update on this.
Went to the BMW dealer today to see the X5 mentioned in the opening post to this thread, didn't really have time but was keen and convinced it was 'the one' having asked loads of questions on condition/history etc via e-mails and calls to the dealer.
The sales guy I had been dealing with all week waas with another customer so this other salesman dealt with me, the saving grace is that he was a rare car salesman in that he was genuine and agreed with what I found and pointed out.
Anyway, all started well, the look at a distance was good and the wear and tear on the front of the car was ok, a couple of very minor scuffs on one corner that would machine polish out the interior was good condition although the seatbelts were grubby and the carpet had been severely wet vac'd (why, unless it had been neglected?).
Then I moved to the rest of the outside of the car and found what can only be described as the crappiest paint/body repair that I've seen in many years to the rear passenger side door !!
The colour match was good, the finish was poor with debris under the paint and lacquer in places and the prep job was so poor that sanding marks in the initial stages could clearly be seen in the final coats of the paint. This was in all directions all over the door, the adjacent panels didn't suffer as bad but had runs in the lacquer in several places as well as signs of debris under the paint.
Moving round the car, the drivers' side rear door had an odd patch on the bottom hinge side of the door, an area the size of my hand with small dents going in and out. My only assumption is that it was 'paintless dent removal' gone wrong.
The sales manager was called out and said that they would do what was needed to do 'a proper job', I said I thought that we are possibly talking new door/door skin on one or both sides and he said they would let their 'skilled' paintshop guys look and give their opinions or methods to put it right.
If I'm honest I think I'm walking away from it, I'm disgusted as I thought that BMW Used cars were pricey but quality and fully checked. I would have faired better by paying 4 grand less at dodgy John's car lot

)
I'll let them suggest what they are going to do to put it right but they will need to throw some serious money and skill at it to get it right, as they've wasted half my weekend with a 150 mile round trip then I'll waste some of theirs
Had a test drive so that was good, lovely car and still convinced I want one, I have learnt though that BMW AUC aren't all they're cracked up to be.
Edit: to save other people wasting their money and time this is the car in question;
http://www.approved.bmw.co.uk/bmwuk/bmw ... fid=401274