What I did was just a credit card with no international fee for the beginning.
I changed my address to my UK address on a couple of my banks so they mailed my statement there. Specifically Bank of America. And make sure to de check paperless.
After about six weeks the statement arrived and I used that as proof of residence in UK and opened up a checking account there (called a current account). I did Barclays in branch. You have to set an appointment there you can’t just do a walk in and say i’d Like to open an account.
Then I signed up for TransferWise at
www.transferwise.com as you can use that to transfer currencies almost fee free (less than .5% as compared to the usually +5%). You can send between your UK account and USA account, and vice versa. Then I signed up for a TransferWise boarderless account and debit card which hooks up to an account that has GBP USD and EUROs. But you have to use your UK address or they won’t give it to you.
Or the USA Fidelity or Schwab account mentioned above let you withdraw from your USA account at UK atms without much exchange fee (they say none but I believe it is actually 1% from live rate.)