The method of payment varies depending on the cruise line but most operate a cashless system. A card will be provided for you to use when you purchase anything on-board and the items will be charged to your account. At the end of your cruise you will be provided with a statement including all your purchases and the total amount payable. You will usually be able to pay your balance using GBP, although other currencies or travellers cheques may be accepted by some cruises lines. For shore excursions, you will usually be able to exchange currency at the reception desk, although not all currencies will be held on-board so please check before your cruise.