on chainreaction you can get the brakes for just under 60 GBP including rotors although right now there only selling 185 front and 203 rear. shop around should find some=]
what about these stroker ryde £100 http://cgi.ebay.co.uk/Hayes-Stroker-Ryde-V8-Mountain-Bike-Disk-Brake-Set-203_W0QQitemZ310104770664QQcmdZViewItemQQptZUK_sportsleisure_cycling_bikeparts_SR?hash=item310104770664&_trksid=p3286.c0.m14&_trkparms=72%3A1688%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318
i have the stroker trails they are better and the only cost £30 more thats 130 for a pair of stroker trails