Banking while in Britain
As a security measure let you bank know that you're travelling overseas. Although there are many banks in large towns and cities across the UK, it's unlikely you'll have to visit one - unless your usual bank is represented in the UK.
If you run out of funds, it is possible to have money wired from your country to the nearest British bank. Branches of Travelex and American Express will also do this for you. North American visitors can get cash dispatched through Western Union to a bank or post office. Remember to take along your passport as proof of identity.