Noba, if you property is registered (correctly) at the land registry, then unless you want them for historical reasons, what the bank has is worthless and you can tell them to take it and stick it if you want to.
But to be helpful.....When My Dh died last year, one of the things I did was get our house transferred entirely into my name and at that point, I found that the charge put on my the bank for a loan around 5 years earlier was still there. I got onto the bank and asked them to remove the charge and they said more or less the same to me, ie have you got documentation to prove that the loan has been paid back.
I had only been widowed for a matter of weeks at that point so i lost it on the phone and said quite brusquely that they should have all the documentation required on file in their office and would they kindly stop behaving like asses (I might not have said asses) and remove the charge to which they no longer had any right. Brief silence, polite agreement to do so. Job done.