Citibank seem to do the cheapest Sterling, Euro and $US accounts which use only 1 debit card for withdrawals and transactions instores, hotels etc. You would need to either call Citibank or send them a secure message though online banking in order to switch the account you wish the debits to be made against. There are no fees then for transactions made with the debit card but check about making cash withdrawals from differnt banks. When I have used my debit card in the USA I have never had to pay a charge for ATM withdrawals.
To transfer a large amount of money, try using a currency exchange firm as they give far better rates than banks and some will even do the transfer with no charges for sending money overseas. Personally I have used Hargreaves Lansdown in Bristol for transfers I have made but there are a lot more Forex brokers out there, try to negotiate the rate a bit higher in your favour when making the actual transfer. You need to provide the usual proof of ID to satisfy the Money Laundering regs as if you were opening a bank account and brokers may not even give a firm quote until you have registered with them as rates fluctuate every second.