I have used airport parking before and have never had any trouble. However, when I parked in the surface car park in December, I spent a lot of time circling round trying to find a space, despite the signs outside of the parking area stating that there were spaces. Unfortunately, I wasn't the only car circling to find a space. Eventually, in the 2nd overflow car park, I found a spot (not a space) between two cars that were parked on the side - luckily I have a Mini so I managed to fit. I spent a lot of my time away worried that I'd get back from my late flight and find my car had been towed away. I feel for the amount of money I'd paid, that there should be a space available to park when it's been pre-booked.