Wendax has found it, despite my misleadingly asking for the maker and engine (implying that the engine was not original) so deserves another point!
I did not know it was for sale and thought it would be rather harder to track down.
As you have found there are/were quite a lot of non-Vauxhall parts about it, so can you think what it is/was called by the owner?
The name recently came up for another car in Autopuzzles!