Est costs would be about for the 4 days at the Ring:
4-5 tanks of fuel
depends what part of UK you are driving from and how many laps of the 'ring you do Or if you have a fuel card that pays for all U.K fuel
£130 tunnel
£60 breakdown cover and insurance
depends if you are already covered on these things
£150 Hotel
£150 beer and food
depends if you have a dave appetite and how many bets you lose
£100 Ring
Tickets how many laps is up to you
£40 Gokarts
again, optional
you can do it cheaper if you restrain yourself a bit.
also not driving a 5L V8 helps a lot as 6mpg around the ring aint cheap!