Hi,
Thanks for the feedback folks. Part of this is to check that I'm not going mad!
Of course I have no issue with the concept of paying back what I owe - I'm not one of the 'money grows on trees' crowd! What I do have an issue with is that, due to them messing up what I understand to be a fundamental part of their job (which is to calculate the correct repayment amounts over the term of an Annuity mortgage), they try to foist this on me with what are essentially balloon payments that I'll go into arrears on if I don't pay them. One theory is that, at a point in the past, they messed up, either when we negotiated a tracker, or maybe when we took out extra mortgage sub-accounts with them (they've all got slightly different terms, but all ending within a year of each other).
When we argued that it's only this small (repayment date adjustment) that has triggered this large repayment recalculation, and what would they have done if we had continued as we were previously to the end of the term: they were honestly arguing that we would have been presented with a bill for the outstanding balance (many thousands) to be paid on the final date of the term. To my layman's brain, this is a balloon payment, which should not happen with an annuity mortgage if the bank is doing its job.
Latest update: On the phone to them today and, having banged my head on the wall with the Arrears people and their "there's nothing we can do" attitude, I finally got onto a manger who is prepared to admit there has been some form of 'banking error'. We'll see where this goes. A reasonable outcome I hope.
And Brendan, thanks for the advice. I will make sure that I get this admission of an error on their part on paper!