Just to give an update.
The Corrado V6 280mm carrier and calipers fitted straight on my Golf 16v hubs but do in fact foul the front/spokes of my 15" BBS RA's. Luckily my 10mm wheel spacers sorted that problem.
The Corrado 280mm discs do not fit though as the offset is out (just as many of you have suggested), so even if I drilled the 4x100 stud pattern it's a no go for the discs.
So I'm going to order a pair of G60 280mm 4x100 discs to go on shortly and I'm all 280'd up!
Thanks everyone