Dan,
If your trip does not work out, I am planning a trip (definitely going) to Salisbury Plain leaving Dorset on 24 Oct and meandering up to the Plain via some byways, etc, camping out on Friday and Saturday 25/26 Oct 08, driving Friday, Saturday and Sunday. Just the normal byways and evening barbecue stuff!
If you or anyone is interested in coming along for all or part, drop me a post for details.
Steve