Many UK airports are suffering financially from the lower landing fees being offered at regional airports which are attracting the low cost airlines. One way of keeping their balance sheets healthy is to rip-off unsuspecting travellers who drive and park at the airport without researching their options first.

The worst example we found was parking your car at any on-airport car park at Heathrow. All of the Heathrow on-airport car parks are owned by the BAA and run by companies for them. The BAA sets the price it wants people to pay when they either pre-book a space or just turn up at one of the car parks.

The difference between pre-booking and paying on the day is as much as 60% and for a two week holiday that can be 60 or more. Now you might think how generous it is to offer such a great saving and you're certainly not wrong about that but the trouble is that most of us just turn up at the airport without pre-booking - captive customers with no time to find a cheaper alternative. If only they had looked online for a better deal.

An alternative to parking at the airport are the privately run off-airport car parks that are often cheaper than the airport's own long-term car parks, and online discounts can make off-airport facilities even cheaper.

Drivers often avoid off-airport car parks, thinking it will take extra time to transfer to and from the airport. But many airport operated long term car parks are also a shuttle ride away from the terminal. And at busier airports, such as Heathrow and Stansted, the long-term car park is often full, which means you could spend half an hour looking for a space before searching for an off-airport car park anyway.

So, the moral of the story is to do your research, compare prices and get the best deal online.