When I got my Golf in 2009 I made very sure all the servicing would be done by my own garage, 15 minutes walk from my house and with a bus stop outside that would take me to work. In 2012 the engine comprehensively failed, just three months inside the 3-year guarantee period.
VW were extremely picky. They made Andrew (the owner of my garage) send every bit of service history. They even made him get and fax copy invoices to prove he'd bought the correct oil for the car. There was a slightly nervous moment while he covered up for having fitted a non-VW air filter at the most recent service (he hadn't been able to get a VW one), but he re-issued an invoice to me which didn't state the source of the paper filter (which he correctly said would not be noticed when the car was looked at by VW) and all was well. New engine for £0.00.
VW were very mean though. They told me I'd have been entitled to a courtesy car if I'd had the car dealer-serviced, but they weren't going to give me one as punishment for using Andrew's garage instead. I spent a week in a crappy Kia that cost me about £120, I seem to remember.