My noise is worst between 30 and 40, but it's there at higher speed too. Pretty sure it is due to stepped wear of the back tyres (50p effect) caused by miss-alignment of the rear suspension. Dealer says that wheel alignment is only covered for the first 6 months and a 4 wheel alignment costs £65! I'm going to try for a "good will" gesture of 50% of the cost of 2 tyres and the alignment, less a bit for the fact that the tyres are 50% worn. Don't know what my chances are though.
Thing is, I've never even bumped the back wheels against anything and I know that new alignment figures were issued around November 2005, a couple of months after my car was built. What was that for? A quick trawl of the internet throws up loads of cases of this noise problem, with varying response from dealers. Just another case of VW avoiding a costly recall IMO.