Run, don't walk, to a local credit union that is part of the NCUA (like the FDIC, but for credit unions instead of commercial banks). And ask about their fees. I suspect that based on their answers you will want to open an account, and get a debit/ATM card (probably will be a VISA one, but I suppose could be a MasterCard).
I have used VISA debit/ATM cards from two large local (NCUA member) credit unions where I do my banking, on two recent trips to London
One CU charged me NOTHING for any ATM withdrawals or debt card transactions. The other CU charged me ONE PERCENT on those transactions. Period. No other fees. And the exchange rates for all those transactions were extremely good; I keep up with the rates on www.xe.com, and I was very happy to see the exchange rates on my CU account statements.
A good exchange rate plus, at most, a one percent fee? I'm fine with it.
And be careful about opening a new account anywhere just before going on a trip. Last year I traveled to Thailand on a small group tour that included a friend who lives in another state. Always canny with her money, she told me she'd opened a new account with some outfit (Chase? Capitol One? Schwab? some mega-sized corporation, I can't remember which), just to get an ATM card which she could use on her travels without paying a fee. Of course, she put a bunch of money into that new account, to draw on during our two week trip.
Good thing she also brought along her "regular" checking account ATM. Because that new ATM card for her new account? Would not work in Bangkok, despite multiple calls to customer service. She never did get it to work in Thailand, and had to use her regular checking account ATM for the whole trip.
Which is why I carry cards for two entirely separate accounts, in my case at two different credit unions. Stuff happens.
Happy trails!