Thanks everyone for the replies..
Well, the weather proved to be lovely today and I had a free day, so I thought I'd get it sorted finally.
After about 2 hours of straining and shedding the skin off my knuckles I finally managed to remove one of the rear hubs/discs. At which point I proceeded to slowly lever the ABS ring off of the old hub.
It eventually came off, so I went to fit it to the Brembo and guess what!?! The air turned pretty blue I can tell you. The ABS ring is about 4 or 5 mm too big!
WTF! Why do car manufacturers do this? I triple checked that I had bought the right discs before this undertaking (with the seller and cross referencing and all that stuff) so am royally chuffed off right now.
I don't have a clue where to turn from here, I am supposed to be driving 300 miles or so over the weekend, but that's no longer happening as there is no way of sourcing other parts until next week really.
They are 44 teeth ABS rings, so my question to anyone in the know is do they come in different diameters, or have I been sold the wrong hubs/discs?
Many thanks again in advance for any response..