The car I originally registered had a mechanical failure the night prior to parking so I went on line and amended the booking with my wife's car registration. I received a confirmation and printed that out with the new details. When I came to depart somedays later, I refused exit and advised I owed £207. I parked again and went to the kiosk. They had no record of the car registration change but when I showed them the printed confirmation they amended the booking to let me out with no further charges. Inconvenient after a long trip and poor weather on arrival in Aberdeen. Disappointing that the booking system never registered the change. Otherwise, iris a good deal.