280mm and 256mm calipers are the same it's just thecarriers that are different.
As I wanted to keep 4x100 on my mk3 to update them I used mk2 16v hubs,54calipers off an early mk3 golf or Ibiza with 280mm carriers off the same car.then used g60 discs and pads.
Unfortunately I've just give someone my 2 spare calipers or you could have had them for postage costs.
If you look for 256mm set ups people not in the know don't charge such a premium when they are intact the same g54 caliper as the 280mm ones.