Mortgage overpayment

Sparkles11

I recently went into my bank as my 2 year interest rate was going to run out and went to arrange a new rate. At the end of the appointment, it transpired that I had over paid (only by my monthly payments set by the bank by over £12,000). I had made some extra payments from a Pension lump sum and one was classified as an 'over payment' and the other as a 'part redemption'. What's the difference and why would the sums of money be processed in a different way? It suits me to have the money refunded but I can't help feeling aggrieved that such an error should have occurred. They have refunded it within 48 hours but would it be prudent to involve the Banking Ombudsman as 5 years ago when I was diagnosed with Breast Cancer, I contacted the bank to ask for an interest only term as after 6 months my salary had been reduced to 50% as the treatment lasted 10 months but they said no, leaving me in hardship for a while. Any advice would be greatly appreciated. Many Thanks