At the end of the day, whilst I feel your grief, I'm afraid you have fallen into a basic mistake.
The car salesperson's job is to sell cars.
No part of that job description is likely to inculde phrases like "be aware of the minute detail of Tax implications" or "be qualified to give TAX or accounting advice".
He may have told you what he believed to be the case.
But if you went to Tesco and asked the person behind the cheese counter if you would be able to claim the tax back because you worked for a sandwhich making company, would you listen to what they told you?
I hope you get it sorted, but unfortunately I think your Dad's accountant is the person with the answers
And as tongie mentioned, might be worth chatting to them about your status as an employee with access to company cars - that can end up costing you big bucks if the car is used for social instead of
purely for work...
sorry!