Mines an early 14 Gti PP, had same problem, cost £785 at a local garage a few months ago. It's a big fiddly job!
Once the Service plan run out, I started taking it to a local non VW garage for it's service & MOT. That, together with it being 5.5 years old at the time, didn't fill me with any confidence that VV dealer would help out as a good will gesture. Plus the car was already at the local garage, couldn't just take the biz away from them.
Earlier this year, I'd test driven an 7.5R at the dealers and got a quote for what they would give as a part Ex for mine. Turns out if you've taken it elsewhere for a service, they couldn't retail it, and thus meant the Part Ex quote was £1K less!!!!
However - Hope you do manage to get some joy with the dealer, good luck.