So turns out I was overpaid after all the jazz and the back payment. (Although this is being re-investigated as it seems wrong).
Grrrr - now I do have the money still in my bank but I was feeling relief as it meant I had all my savings for surgery. So now I'm wondering if it turns out I have indeed been overpaid - does anyone know the rate at which I would have to repay it??
It's near $3000