No Limits Trackdays use Paul Russo, as do a number of the other trackday companies. Paul has about 10 R6's, all totally race prepped with race cans, bodywork, rearsets, decent suspension etc etc. I've ridden several of them (he uses us to test them after crashes or to run in new tyres - dummies or what???), so I can personally testify that they are good bikes.
Paul supplies everything and personally looks after the bike all day, unlike some other rental firms, so he will fuel it up and put the tyre warmers on after every session - you just turn up and throw your leg over it.
Send me a U2U and I'll give you his mobile number.