Whilst searching for the parts required to do the rear leccy window mod (thanks again Roy (lofty)) i found these people, they had everything i needed and they seem fairly reasonable aswell.. Most of the parts i was after have been sourced from a 3.2GSi, i asked and they said it was almost complete so if your looking for GSi parts they may be able to help you out..
If you say your from Vectra-c.com they might even give you a discount..

http://www.phoenixspares.com/