Rugby Scene in Carnaby St do a 10% discount on presentation of a 1250 (or whatever the new fangled version's called) and are one of the few places you can still try on a decent range of boots, now that most "sports" shops are more interested in leisure wear or fashion... They're quite friendly in there and apparantly get a good few of our Fijian comrades through the door. I dare say Soccer Scene, their sister shop immediately below also offers the discount, but I can't imagine myself ever pressing to test.
Incidentally, they're giving away free G&Ts in Victoria Station as I type; only Gordons dispensed from a premixed can, but a refreshing bonus nonetheless.