Just Google the companies, there are a few but use a reputable one, I rented a road legal track prepared 330 bmw off a company in 2009, can't remember there name but can find out if you want to. Loads of lads use rent a race car and get something like the swift sport or Clio rs for there first trip, just make sure to establish the excess, it was 10 k in our car so if we crashed I was fooked,
If you crash your own car there on d ring insurance won't cover it even though it's public road,
That said it's brilliant place,hope to return this year????