It’ll come as no surprise to learn that for destinations in the United Kingdom and on board your P&O Cruises ship, the currency will be in pounds sterling. However, the currency in the Republic of Ireland (which is part of the geographical term ‘British Isles’) is the euro. With stops at Irish destinations on a P&O Cruises British Isles holiday, it’s a good idea to have enough euros to cover any food, drinks, treats or souvenirs when you’re ashore.