Thanks all. It is drying, slowly..very slowly.. The car I have has a kerb weight of 2.6/2.8.ish. Looking at all of the replies I think my only choice is to let it dry, then drive on it and see what happens. Worst case the car will break it up for me, easy shovelling before getting someone to come and lay some more. Otherwise it means pulling it up damp, and I can only see that making one hell of a mess. The builders are long gone...cash on the side job as he was finishing doing something else. My own fault there. :-(
