If anyone is needing new tyres soon, the Michelin PS3s are now only £108 a corner fully fitted, and they have a promo on for £30 cashback (or was it a Costco voucher?) on a pair, effectively making them £93 each fully fitted.
GTI-J: They use a variety of tyres, mainly ones that are obsolete from a retail point of view. The variety is so they're not putting all their eggs in one basket, only having 1 supplier. 3 or 4 different suppliers ensures they're always assured of a reliable supply.