Correct me if I'm wrong but from what I know they are the following
8V pre-facelift <97 are 239mm from the MK2 Golf Gti
8V Post-facelift 97-99 are 256mm from the Mk2 Golf Gti 16v
1.8 16V are as Chris says 256mm
All 2.0 16V are 280mm Disc's with golf G60 Calipers which have been the essential brakes on any Tuned VW for as long as I can remeber!
You're wrong
all 2.0 8v's have 256mm brakes
1.8 16v have 256mm brakes
2.0 16v have 280mm brakes