Ive just booked mine into a local garage, there reckon 50 pound a side. Had exact same problem, took to local Watling Tyres unit, and was told it was suspension arms, so replaced and noise was worse!
Rear axle bushes common problem, had a look at fixing myself with this DIY guide :
http://forums.vwvortex.com/zerothread?id=1980960However when it mentions removing brake lines etc... no thanks...
Good luck mate, mines being done Tuesdaym bloody annoying noise though i must say.
Josh