So rented a car from RentalCars. Flight cancelled, the next delayed so picked up a day late. Talked to RentalCars via Skype and they were fantastic, no problems, cancelled first and then rebooked.
However when I picked up the car at Malaga, the people there didn't know what I was talking about, then found my booking but still charged me, not much but some, for 'administration', I also took their insurance deal. So all in all £164 for 9 days, £123 of that for insurance. Not bad but still not sure how this is supposed to work.