My friend was 5cm dilated when she got to hospital and she still had 6 further hours of labour so you won't necessarily give birth in the car!! When is your next OB appointment? Maybe you can bring it forward if nothing happens in the next day or so.

By the way, you said you've had a bit of a show for the last few days. Does that mean my 'bit of a show' is going to last a few days too? I was praying it would mean labour by tomorrow!!