Unfortunately these sort of mistakes happen all the time I had to pay a bill 3 times last year for tax & NI on my board operators earnings every time i paid it they credited the money as payments on account for this years tax even though the amount was the exact amount on the bill and paid according to their instructions. And after i finally got the the IR to credit the money properly instead of threatening with legal action i asked them about the overpayments they wont refund that untill after the PAYe returns have gone in this year and I am not allowed to deduct it from payments due
There seems to be an overly agressive stance by the revenue these days over money they think they are owed and they don't seem to give a stuff about the impact that has on the lives and businesses of the people they are dealing with 10 years ago it was differet you could deal and negotiate with them
perhaps its high time that IR inspectors became subject to the same corporate responsibilty rules as company directors and face prosecution if they make errors as serious as the one which has destroyed this poor blokes life