As the mercury rises across Britain, many will be thinking ahead to their summer getaway. But now a new study has revealed a simple airport mistake which could be costing Brits nearly £300 without them knowing. New research from eurochange has found Brits could be losing out on hundreds of pounds worth of spending money just because they bought their travel cash at the airport.

The study found exchange rates at airports can be up to 13% higher than on the high street or online, costing Brits dearly. The most expensive among the airports studied was London Gatwick, where Brits exchanging €1,000 could lose out on a huge £274. Even at London’s Heathrow airport, where buyers can secure some of the best rates of any UK airport, travellers were still found to be overpaying by more than £100 when compared to high street or online rates. Laura Evans-Fisk, head of digital and engagement at eurochange, said: “It’s surprising to see the vast difference in rates across UK airports, and the huge amount of money Brits could be losing out on if they wait until they get to the airport before exchanging their cash.

“Changing money at the airport is absolutely the least cost-effective way of picking up your holiday money, as rates can be up to 13% higher than they are on the high-street or online. As it’s often a last-minute necessity, customers are forced to convert their cash at whatever rate is offered to them in the airport, whereas on the high street, they have more options.”

She added the best time to buy travel money was during the week, when business is quieter.

“Typically, Monday through to Thursday is the best time to buy your euros, as these are the least busy days for transfers, so you might see a little less fluctuation in the mid-market rate over these days.”

Gatwick was closely followed by London Stansted and Birmingham airports, which saw travellers miss out on £264 and £156 respectively when exchanging €1,000.

When exchanging US dollars, though, Stansted came out as the worst airport in the study for helping travellers save, with a missed saving of £252 on $1,000.

Dropping down significantly, the next biggest culprits for losing out when exchanging dollars were Edinburgh and Birmingham airports, with £151 and £150 missed out on respectively for $1,000.

The best-performing airport for dollar exchange was London Luton, though passengers passing through that location still lost out on £102 when exchanging $1,000.

See below the full list of airports (savings missed out on per €/$):

Birmingham (£156/150)

Edinburgh (£152/151)

London Heathrow (£108/148)

London Luton (£126/102)

London Stansted (£264/252)

London Gatwick (£274/111)

Manchester (£153/148)

Glasgow (£139/133)

Liverpool (£124/122)