Was on a flight from Copenhagen to Stansted yesterday and the people next to me bought 2 coffees. The stewardess asked for £5GBP and when they asked to pay in Danish Krone, she told them that it would be 100DKr.
The exchange rate is approx 9.5DKr to £1GBP - this means that they are charging around DOUBLE the accepted rate.
I am not sure if anyone can confirm whether this is normal practice, but I had to intervene and suggest the passengers pay by card.
Nothing short of theft.