I was driving all the way to Budapest and back so the cost of petrol was significantly higher than it would be just to the 'ring. If I recall correctly it's about 700 miles there though so you could probably get a rough idea based on that. And I can't remember the cost of the ferry although I'm sure you could find that out off the P&O website or something?
I'm reasonably well trained as far as track driving goes so I didn't find it terribly daunting. The important thing to remember is that in lower powered cars like these you
will be getting in people's way so just keep checking your mirrors so as not to water falling anyone off and be sensible. I can't stress that enough and it only really hits you when you see cars that supposedly represent the pinnacle of what a car can achieve, Porsches/Lotus' etc, smashed to pieces at the side of the track or in one of the car parks.
It's also well worthwhile to check that your car's brakes are up to scratch and carry a spare set of pads with you as, depending upon how many laps you do, you'll probably wear atleast one set out.
Last but not least don't forget to pick up a sticker for the back of your car
I'll hopefully be back there this summer too, I can't get enough of it.
HTH.