In fairness I would be happier to hand over my cash for a car that does have a Full Service History, not necessarily a VW one, as long as it has all the MOT's & Receipts to back it up...
I keep a copy of every receipt for every nut and bolt I buy, and stick it in a folder, not to increase the value as such - but just to give the car some serious history and that I'm anal too!!!
I have just forked out £500.00 (G60 Shocks, Front & Rear Discs, Pads, Rear Bearings, Rear Caliper Carriers, CV Boot Kit Etc) on bits for her from VW and a copy of the bill is already in the folder.. I will attach the mechanics bill to that when I get it, and then it also ties up when the items were in fact fitted!!