Our checking account is with USBank, as is our Debit card for ATM withdrawals. To avoid or minimize bank fees as much as possible, don’t get Pounds from your bank at home, and don’t go to any currency exchange counters or their “ATM’s” at the airport after you arrive in the U.K. Go to an ATM out on the street in town, or in an actual bank (not an exchange service company), and withdraw funds there. While Britain is becoming increasingly cashless - pay by credit card as much as possible - we still found places in London who took Cash Only. Pull out only £100 to £200 from an ATM, and see how that lasts you. Go back for more cash if needed later, but limit the number of times you make withdrawals, as there’s a fee for a Non-USBank-ATM charge with each withdrawal. Generally, make fewer withdrawals, but for larger amounts of cash each time.
Yes, have credit card transactions rung up in the local currency. You won’t have to request Pound Sterling, as most (if not all) of your transactions will automatically get rung up in Pounds. The dollars versus pounds issue will only come up if the merchant offers you the choice, and I’m seeing less and less of that Dynamic Currency Conversion (DCC) being used, where their bank adds a fee for the transaction, in addition to yours. If that choice should be offered, stick with Pounds.