I normally use the Post office. I would recommend using an ATM in the USA, my bank would let me take out money for nothing and it had reasonable exchange rate. Got money out in US, Australia, Italy, Ireland, France, Holand and Belgium but when I came back from Spain they told me I would be charged an additional fee for transaction via ATMs worldwide ... I hate my bank
Just checked out the Euro rates
PO: 1.3975
M&S: 1.417
Sorry the Euro rates were for my benefit - on the move later this month, US dollar rates:
PO:1.8363
M&S: 1.856