There is no extra charge, and the bank will earn the middle price difference. Foreign currency is divided into foreign exchange and foreign currency cash. These two prices are different. See if you are in cash or foreign exchange. Based on the listing price of the bank on that day. There is no listing price on Saturday and Sunday. Remember to go to the counter and ask what the price was at that time when changing. However, the price of the pound has not fluctuated much these days. You should be able to change it. Remember to bring your ID card. If you don't have it, you won't get it.