Depending on how long you are going to be in the UK you might still want to consider looking into a student account so you won't continually be charged a conversion fee from your US account. Also since the dollar exchange rate is not at its best it really might be a good idea. I am planning on opening up one there when I start my masters in London. Maybe take a look at some of these articles if you want to figure out the system a bit more before talking to more banks
http://uk.moneto.eu/investment/student-accounts/benefits/
http://money.uk.msn.com/Student/accountscardsinsurance/student_accounts/article.aspx?cp-documentid=4753836
http://www.thisismoney.co.uk/student
Hope that helps