I'm glad to see that there was a positive outcome to your problem jamster, especially as I now find myself in a similar situation.
I bought a 2007 plate 3.0 si in January 2011 from a main dealer through (what I believe was) AUC. I remember at the time the salesman was spouting on about AUC and the fact that the car had service history, 12 months MOT and 12 months AUC warranty. I got caught up in the whole 'buying a z4' and foolishly didn't bother to look into service history in any great detail (yes I know this was stupid), i just wanted the car and put my entire faith in the fact that I was buying from BMW AUC.
When I bought it the car had 26055 miles on it and the inspection counter was saying 'inspection 9000 miles' (as I recall). Since then servicing has been at the back of my mind until last month when I noticed it saying 'Inpection 500 miles'. Unfortunately I've been doing lots of miles recently and not had any time to book it in for a service and it's now showing as 'inspection -475 miles'.
The big problem now though is that I can't find the service book... at all. I don't ever remember even seeing it. So basically I have no idea what service(s) have/haven't been done... Slightly more worrying is that I cant even find any documentation that actually says the car was bought as 'approved used', all I have is an invoice that says 'USED NON-QUALIFYING VEHICLE INVOICE' on it, but I'm not sure what that even means.
I know some of you may read this in disbelief at how I didn't check service details etc. but I kind of bought my car as an impulse purchase, its only now that I'm panicking that I've screwed up... I think back then I thought BMW dealers would be honest and trustworthy, but having loitered on this forum for the last 16 months I've come to learn this is often far from the case.
I'm planning on calling the dealership tomorrow to ask about the service book/history but at this stage I'm not holding out much hope