Mark, if you phone Justin at the TTshop 01234 853 225 (sole distributors in Europe for OSIR), he can give you costs etc. Feel free to mention my name Robin (red Mk5 GTI).
Your cheapest option may be to get a pro bodyshop to smooth the upper part of your standard GTI spoiler and paint it and add an OSIR stick-on CF exhaust trim, but costs are possibly close to the R32 spoiler option.
