As others have said, it depends on how much more you will travel. I have a Schwab Bank debit card which charges no foreign transaction fees and reimburses any ATM fees. The latter is not important for the UK and Ireland but is useful for travel within the US! As to the currency used, I had a couple of charges in Ireland which accidentally went through in USD and the premium was about 3%, which can mount up if you are paying for hotels, etc.