Everyone's advice about calling to sort it out is entirely correct, but I wanted to give a few more details. the internet prices your tickets in euros because it is organised to automatically ticket the flights in the country where they start. The call centre allows you to have UK-ticketing for a flight starting in, say, Germany. There are, however, some potential inconvenients as well as advantages depending on where your EC account is located. Inconvenient in any case is that occasionally, some promotional fares are only offered if ticketing takes place in the specific country. It happened to me with one CW flight last year at least. An advantage/inconvenient is that should you wish to use your avios to upgrade or anything this is theoretically only possible if the ticketing is done in whichever country your EC account is located in. Apparently, occasionally the call centre agents don't realise that and still force it manually but this could also be refused if your account is, say located in Germany but you ticket in the UK (or vice versa).