I'm pretty sure camping is an extra but I'm sure someone will be along shortly to confirm this.
In the mean time I found this on the AITP website...
How much is camping and how do I book?
All camping enquiries, including prices, must be sent directly to www.billingaquadrome.com or telephone...
So maybe meet at Cherwell Valley Services at 7:45?
Go up the A43 then on the M4 South to Junction 15 then on the A45 to pick up smirky from the Shell Station at NN4 0JN at 8:15ish
Then head to AITP for 8:30ish?
Only my thoughts as I'm happy to tag along with everyone else.
I can meet you at Cherwell Valley Services on the M40 Junction 10 if you like?
I think there are a few people coming from Slough / High Wycombe up the M40 so it could be a potential meeting point for everyone?