Can't go wrong with either the Schumacher or the Hot Bodies really.
You could get the S1 Mi3.5 and upgrade as and when you have the budget. Or you could get the Cyclone S, and do the same, upgrade as and when you want.
Mr Skelding ran a Cyclone S at Don Valley last year in the mod class and gave the fully raced up Cyclones and good run for their money.
But I think whichever you go for, it'll be a BIG step up from the TT-01.