Can't help you with the bike hire, but if you're planning to go the TT in 2007 you really need to book now on line at
www.2007tt.com if you haven't already done so - £20 per person deposit. I believe the ferries are already 90% booked and filling fast. The prices will be approx the same as this year plus a few £'s I paid £168 for a bike + rider for this year's TT, the foot passenger would have been in the region of £70. What ever the IOMSPC charge, you won't be disappointed, this years TT was absolutely fantastic. I booked for 2007 last year. Get your deposit paid now and stuff the expense.
See you there
Charlie2