Where about do you live mate?
I've been loads, I live in Liverpool so we always do the Hull - Rotterdam overnight ferry. Easier on the driving and the ferry is a properly good laugh!
The boat is about £280 for a car and 2 people. Then fuel depends on the laps you do etc. Its roughly 250 miles from Rotterdam to the ring.
There is loads of hotels, normally about 40 Euro a night, we got a lovely chalet last year though by the new test centre which worked out fairly cheap! Then your laps and spends, think laps are upto 27 Euro a lap now!
One of the BEST trips you will ever do though mate! It's a petrol heads paradise.