Theres 2 ways of doing it.

The first :

Use 2wd 4 pot calipers combined with standard 2wd cossie discs (283mm). (this is what i have done). To do this, you need to have 3 or 4mm machined off the mounting face of the caliper where it bolts to the hub. This is so that when the standard 2wd Cosworth disc is sat on the hub, it is in the middle of the caliper where it should be. I suggest machining 4mm off the caliper, and then if necessary, space the caliper using 1mm washers if you feel that the disc isnt in the centre of the caliper (all cars are different remember). The only other issue really is that the 4 pot mounting holes dont quite line up properly with the holes in the hub. The top hole lines up perfectly, but the bottom hole in the hub is slightly lower than the hole in the caliper, so all you need to do is elongate (lengthen) the hole in the caliper so that it lines up with the hole in the hub. You will end up with an oval hole in the caliper, but that doesnt matter. Also, you need to tap the two mounting holes in the hub using an M12 tap, and then use a pair of M12 bolts to attach the caliper. The final issue is that the position of the brake fluid hose on the 4 pot caliper is very close to the driveshaft on the S2, so a new set of braided hoses need to be purchased which have a banjo fitting on (basically making the brake pipe a 90 degree bend out of the caliper to avoid the driveshaft).

The second option :

Use 2wd 4 pot calipers with special discs on alloy bells which have the correct offset to fit onto the hub with an un-machined caliper. The reason i chose not to do this is for two main reasons : the discs cost a lot (£285 a pair i think), and you have to file the pads slightly before you fit them to ensure they dont rub on the alloy bells. The same applies with this setup as above with regards brake pipes and mounting holes etc.

For the hoses / mounting bolts / brake pads / discs etc etc, contact Mike R at mike@rjpipe.demon.co.uk and he`ll sort you out.

Incidently, I have the correct brake hoses with Banjo fittings for sale, brand new and un-used from Mike R