Since the USA will be your destination there are a couple online places to find surcharge-free atms.

One is http://www.allpointnetwork.com/

another is http://www.cudollar.org/

If your own bank in the UK has a US network it may have free atm's also. HSBC Premier, for example is surcharge free and also FX fee-free fro HSBC Premier customers anywhere in the world. I bank with HSBC partly due to that benefit.