Which? carried out Exchange Rate research on the main airport bureau de change providers and found that they offered substantially better exchange rates online compared to the rates available at the airport.

Which? warns holidaymakers travelling overseas that "they could lose out on their foreign currency" if they make their exchange at an airport.

Researchers compared exchange rates offered at Gatwick, Heathrow, Luton, Manchester and Stansted over a six week period and found the exchange rates available in the airports were significantly lower than the rates available at the same time online or on the high street.

From the table above it is possible to see that Moneycorp have the most significant difference between their online and airport exchange rate. Exchanging £500 into Euros with Moneycorp would give you on average 518.42 Euros at the airport or 569.82 Euros if you bought online. That's a whopping 51.40 Euro difference. On BBC's Watchdog show recently they reported on similar findings and contacted many of the currency providers to find out why airport exchange rates are so different to the exchange rates available to customers online. The general response was that the cost of operating within an airport was greater and this had to be reflected in the exchange rates available to customers. However the lack of competition is also likely to be a significant factor. Traveler's arriving at the airport with no foreign currency have no choice but to buy currency from the airport Bureau de change.