Outrageously expensive car rental

I made a reservation for a Europcar hire via a link on the Air Berlin homepage (Reservation no. 921851317) on 02.03.2012 for the 5 day period from 5th to 10th April 2012. As I had previously made several reservations at reasonable prices with this hire company I did not see in the small print that the 5 day reservation of a 2 door Corsa was going to cost me 738.30 pounds sterling! I only realized this at the Europcar front desk at London Stansted airport when I picked the car up on 5th April. As I had an urgent appointment that evening I signed for the car hire in the hope of being able to negotiate a refund with Europcar customer services. To make matters worse I specifically asked at the front desk if the car had 4 doors and I was told "yes" only to find that I had a 2 door Corsa, which was extremely inconvenient because I had to pick up elderly relatives. I have since been in touch with the UK customer services who told me it's nothing to do with them because I hired the car on a German website. Germany customer services wrote to me that they can't offer me a refund without approval from the UK! Hence my message to all my family, friends and work colleagues is "Don't hire a car with Europcar unless you want to subject yourself to a non-refundable daylight robbery!" I feel like I've been mugged, in fact the whole affair ruined my Easter weekend.