In reply to airborne:
I used Morphis a year ago because they were cheap. I then proceeded to screw up at every opportunity: I gave them the wrong pick up time, so they rushed the car out to me early. I put a huge scrape into one wing whilst parking, and they charged 450 euros (less than half my excess). I then dropped it off half a tank of fuel short because I missed the last garage on the way back into the airport, and handed them a 20 euro note to fill it back up - they were fine with that.
They were so unfailingly polite, helpful and reasonable that I can't imagine they'll stay in business long!