Superside
I've been to the TT 'once or twice' (since 1954 as a little kid actually) and you will be fine with a van, loads do it and as long as your ticket is valid for the vehicle you arrive at the boat with you won't get any hassle. "They're far to fookin' busy"
The campsites are getting booked up but there are many sites on the IOM Tourism web site (Google)....but the best are probably Glenlough, just past Union Mills, the Douglas Rugby Club at Quarter Bridge. Both are accessible to and from Douglas at night, and both have very strict noise regs. so no bikes revvin' their nuts off at 3 in the morning. Glenlough and the Rugby club both have their own bars and Glenlough serves hot breakfasts and has many hot clean showers. I have heard they are putting on some entertainment this year as well.
If you are not tied to Douglas for nightlife there are other great sites at Peel, Kirk Michael (The Glen) and Sulby Glen (very international)
PS Martyn....first TT 1907 - Centenary 2007. The hundredth TT wouldn't actually be next year either because of war years. There is also another Centenary to be celebrated for 100 years on the "Mountain Circuit". The Centenary this year commemorates 100 years since the first races on the original circuit around St. Johns.