[Harry-G]

Thanks for the replies.
The metal tag is still on the diff and has been confirmed as Sierra Cosworth. The diff is currently with Quiffe who are fitting ATB internals and they confirm it is Sierra Cosworth.
I've trolled through the Need for Speed website and Gareth's comments are correct, the 273mm diameter discs are Sierra Cosworth but 4 hole.
What I can't understand is that I seem to have a caliper and mounting lugs for a Sierra Cosworth but with a 5 bolt hub.
Harry