We from Stone have booked the 11.45pm ferry on the Thursday with cabins and a return on the Sunday night again with cabins for a grand total of £1009.
Thats 2 cars and 2 double stacking trailers, 3 double and one single cabins (7 people) both ways.
Accomodation is being sorted by one of the other Stone massive, but i believe all the local hotels are booked so its a 10Km taxi and 60odd euros a night for a double room (iirc)
Hopefully its going ahead as the ferry is non-refundable!!!!!
Ferry is cheaper if you do the day crossing, but then its extra nights in the hotel so this negates most of the saving.
The only real issue is the ferry gets in at 745am on the Friday, but not sure what time the first race is, could be a bit tight