Right!
Call me the necromancer but I've been away for a bit (nothing nefarious I assure you) and thought it time to resurrect this thread to see if I can sort this issue out.
Firstly, thanks for the responses and sorry I didn't reply sooner.
I need to source the carriers to convert the old 239 calipers to the new 256 compatible ones.
Here are some images of the calipers and what's really handy is that they're for opposite sides of the car

. The yellow ones are the new ones, the others the old.



Can you tell from these whether they are for the 239 or 256 discs?
Are these images useless?