You won't get through much fuel and I'm guessing most people will run with as little as possible in the tank. If there's a not a petrol station nearby, you could always bring a full jerry can to use at the end of the day.
Hi as Dave says run light and bring a jerry can. The site allows jerry cans and refueling in the pit area.
There is however 97ron about 10 mins away on the A47 Swafham BP and in Swafham Somerfields.
If you need local info let me know this is on my door step