All those duty-free cigarettes and jumbo bars of Toblerone really do add up according to research out today, which shows that British travellers have collectively frittered away £800m in unwanted foreign currency at airports over the past five years.

The average UK holidaymaker dumped £48 worth of currency on last-minute purchases before flying home during the period, while over 300,000 big spenders are estimated to have shelled out over £1,000 at airports. Based on UK duty-free prices, £48 nets you 13 giant bars of Toblerone, one and a half bottles of Chanel No 5 perfume or nearly five litres of vodka.

Perhaps surprisingly, men were found to be the highest spenders of leftover cash, offloading 65% more surplus holiday cash than women, spending £61 on average versus £37.

Perfume and aftershave, followed by alcohol, food, souvenirs and cigarettes were the most popular airport purchases. Books, cosmetics, CDs, jewellery and DVDs also made the top 10 items picked up on impulse, according to the research commissioned by Halifax Travel Insurance.

Once spending using credit cards and travellers' cheques is accounted for, Britons collectively shelled out £4bn on unplanned airport purchases in the past five years, an average of £183 per traveller, according to the survey by market researchers TNS.

However 50% of those questioned admitted to going away without travel insurance.

What else to do with leftover currency

· If you bought your foreign currency at Thomas Cook or the Post Office they will exchange it back to sterling for you commission-free, though low-denomination coins and notes may be refused

· Put most of it towards your last hotel bill, leaving less in your pocket to spend at the airport

· If you're flying British Airways, Cathay Pacific or Qantas, you can make an in-flight donation to Unicef's Change for Good campaign. Back home, donations can be made at Travelex bureaux de change in UK airports or sent to Unicef (unicef.org.uk) directly at: Change for Good, Unicef UK, Africa House, 64-78 Kingsway, London WC2B 6NB

· Some other charities including Marie Curie and Oxfam also accept donations in foreign currency