I love my TransferWise debit card. I got it before my last US/Canada trip (last Christmas). You deposit money in whatever currency you want. It is stored in separate currency 'pots' you can top up any time. If you forget to top one up and use it in that country, it pulls from the pot with the best exchange rate.
There is an app which makes it easy to move money back and forth.
It's not FSCS protected like UK banks/building societies, so if they go bust, you lose the money. So I only top up when I'm traveling. I always have the card on me with roughly £100 as an emergency card if something happens to my debit card.
Oh, and each pot gives you bank details for that country- so people in that country can transfer money to you.
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