I used a car and a basic bike trailer. That was ok at the beginning, except for when you forget about the trailer
. Also when coming back at night you will spend a lot of time looking backwards to make sure the trailer is still there.
Hiring vans - across the year you will need to hire one not just for the races but track days, taking the bike to the mechanic\whatever.
Purchasing a van, hopefully you should get a fair amount back if you are carefull. Fuel consumption is not great. If you are going to use it for sleeping in as well as transporting the bike then something with a little height\length will be more comfortable.
Mark