Did this mod to the front of mine this week. They are a straight swap.
I paid £37 for mine from Ridgeway Newbury VW. There are two types of this valnce though!! One for the 4 Motion and one for the 150bhp GTi TDi. The difference is the 4Motion one doesn't have the vents cut out and the TDi one does.
Part numbers: 1J0 805 903 D (Diesel one I think)
1J0 805 903 F (4 Motion)
Two screws at either end (in front of front wheelsin wheel arch) and pull off!!