Being Avios rich, and having no difficulty in earning the annual 2-4-1 on my BA Amex PP, I took out a Starling Bank debit card for overseas transactions. No more 2.99% add-on by Amex, Starling just charge the MasterCard rate.
Been running it for a week in the USA seamlessly in stores, bars and restaurants. Nice App on the iPad, updates almost immediately after a transaction so you know where your cash balance is all the time. Well pleased.