I bought my 04 Z4 privately and saved a packet on the retail price. Its 45k and in amazingly good condition. The seller said he had waited until the extended warranty expired before he sold it. I have read the posts on here about the various things that can go wrong with Z4's and whilst they seem generally reliable, I was a bit worried that if something major went wrong, I'd have to fork out. I called BMW Warranty and spoke to a helpful fella who asked for the vehicle registration number and confirmed that the previous owner had taken out the extended warranty and also (which was reassuring) that the car had not had any major warranty claims. He offered to reisnstate the warranty for £39.00 (on a monthly direct debit until I decide I dont want it anymore) and whilst it might sound a lot at first, I am now much less stressed about anything going wrong. It has the usual service type conditions and exclusions but I'm happy with that, even taking this into account, it was cheaper to but privately and reinstate the BMW warranty. Just thought I'd share this incase anyone wants to do the same.