Hi Matty.
As Craig has suggested I was doing an adapter using S3/S4 callipers and Pug 283mm rotors. I'm going to use this on my current RS project and has been used a a couple of other cars with greqt success. Unfortunately I will not be producing any more at this stage.
Saying that, Ash on this forum had the original idea of using the RX7 calliper with the BMW rotor - see here
http://www.classic-ford.org/forum/topic.asp?TOPIC_ID=538&SearchTerms=RX7%2CBMWMaybe you can contact him regarding the adapter?
If the above is not relevant to your application maybe you can provide the rotor diameter and the offset of the calliper from the strut (to be centred on the rotor) and make an adapter to suit?
If you are able to get the measurements it would be easy to model it and get it profile cut (2 x 8mm brackets and 2 x 5mm spacers).