Lisa - I think you should get onto Barclays and get them to set up a plan where you reduce your overdraft by an agreed amount each month - say £50 or whatever you can stick to. All you need to do is make sure you keep the fifty quid over so the balance can be reduced without incurring more charges. Soon you will be overdraft free and saving £50 a month.
Changing your banking to HSBC may result in Barclays demanding all of your overdraft money in one if they decide to close your account in light of your claim for unauthorised overdraft fees.
Hope this helps.
JJ
You gotta tie yourself to the mast my friend, and the storm will end.