Is the chassis from a production car like the MG YA or is it from a specialist like Buckler?
A specialist company.
I think I owe you an apology, and this is extended to any other member who has attempted this puzzle. I note that my fellow editor carnut posted an "edit" yesterday and it's possible that he knows what car this is, and considered pointing out the error of my ways! Maybe not - maybe his finger slipped!
I've fallen for the old trap which has caught me before. I didn't check my notes. For some reason I had it in my head that this was a Buckler chassis, and it isn't, and now TT has his answer to that query. It is however a well-known specialist constructor of the period.
I feel it is only fair to add that I'm even more certain that this is a Microplas Mistral shell, although I don't know why it has been modified at the wheelarches, unless it was to accomodate the unusual wheels. It wasn't, as I pontificated, to accomodate the chassis. This is a huge clue.