Try M&S mate, I always find them pretty competitive on tyres, when I saw you on Saturday I got a BT020 fitted to the front of the GSXR for about ?85, mytyres.co.uk list it at about ?78 just for the tyre!
Gary got a full set of 090 fitted to his older GSXR (18" rear) and I think it was under ?180 the pair.