Thanks SR.
So looking around this doesn't appear to be uncommon and not just on Golfs. Quite a few with cracks in exactly the same location so I can only think there must be a design or fitment issue. Also worrying is the amount of strip down some are reporting. Just hope the dealer and VW are reasonable about it and do the right thing, clearly I've not caused the damage and it's not from any impact. Then if and when it gets fixed, will it go again??
Cross posts - thanks TurboTrev, I'm expecting resistance, hoping for common sense.
Monkeyhanger - thanks, good point for me to keep in mind. You'd expect the car to be able to take a shock without the roof getting damaged!