In reply to nigel n:
FWIW after an experience with a hire car (not van) I'd always go with their insurance and just price it in. A group of us hired a car in Italy a while back and did take their insurance (the reason for this being that the main driver of that car didn't have a credit card so they insisted on it) and unfortunately we did quite badly damage it in an accident with a tunnel wall (though still driveable). I had to return it and was nervous as hell about how awkward it might be to explain, and they just said something like "hmm, let's check...yes, you've taken the insurance, so no problem" and off I walked as if it was pristine.
When you've got a flight to catch that has huge value in my book.