There is a general feeling that banks are charging excessive amounts for the fees which they charge. As the won't admit to how much revenue they make from them, you can be fairly sure that it isn't insignificant!! I think that the banking regulator is looking into the issue.
With an increased focus on these bank charges, banks are being a bit more flexible. I managed to get �100 back in fees, when I missed a DD payment for a credit card bill.
The approach that I had taken was I told them I thought that it was excessive, as it was the first time. I threatened to talk to the banking regualator, and to go to the media (ie WatchDog or the newspapers, this a typical Daily Mail kind of a story!!!), also threatened to take my banking elsewhere.
After a bit of arguing, I got the whole lot refunded. I am not sure that you will get them refunded for the last 6 years, but recent ones should get refunded, in the current climate.
Here is further advice on reclaiming bank charges;-
http://www.moneysavingexpert.com/cgi-bin/viewn ews.cgi?newsid1141050760,24632,