I think a mass withdrawal of funds from UK banks may have the opposite effect on charges to customers. From what I recall most UK banks still have a liquidity problem particularly in terms of meeting the new FSA rules on liquidity. This could lead to a shortage of funds available to borrowers and we all know what happens in situations where demand exceeds supply.
A mass withdrawal of funds may well exacerbate an already difficult situation.
Having said all of that, I have very little sympathy with banks particularly the way in which they have performed over recent years.