A few years go, I had issues with HMRC and useless accountants.
I came under audit, and the accountants I used had a few pilots on their books. So I made the (wrong) assumption that they were fully capable of providing the services I was to be paying them for.
Turns out my accountants were claiming things for me that were not supposed to be claimed for. HMRC had an argument that you can't claim for a new qualification, just an extension / addition of a licence / qualification that you already have. The accountants shrugged their shoulders and said I have to pay it back.
When I asked how'd that happen, I pay you as the experts, to assist and get the information correct. They said a new case law had passed and I sign to confirm, so therefore responsibility lies with. Ok, thanks, money well spent!
Little faith in accountants, less in HMRC.
It is a good way of saving some money, but anyone considering it, make sure you get a good accountant, or at least know what you are entitled to as it can come back on you, and they won't just stop at that years audit, they will go back.