Defaulted account & retrospective claim

Sassafras

I had an account with HSBC which I got into some difficulty with when I got divorced. I wrote to the Bank, I visited the Bank but nothing would stop them charging exorbitant charge upon charge upon charge. Eventually, it defaulted and is now with a debt collection agency. I have negotiated to repay what I can, stating that at least 50% of what is owed on the amount is unnecessary historic bank charges , but they won't budge. They want the full amount.
Is it possible to claim the charges back from HSBC even though the debt is with a debt collecction agency?
Nothing would give me greater pleasure than to pay them off with their own money.

Also, I had a similar situation with Abbey National but I have paid them off. Would I be able to claim, even those this is settled and closed off?

By the way, you must have them on the run. I had gone overdrawn with Nat West by a day, 2 weeks ago, & I asked them to waive the bank charge and they immediately said yes.