That's a fare point Carnut, and in truth I'd forgotten that H R Owen had already been mentioned, as this puzzle has caused so much interest and debate.
So, I'll close it off now, and add the final bit of information, which is the base car, which was planned to be the AC 428 model, using the 7-litre Ford V8 engine, mid-mounted.
The car was planned as a 2+2 with gullwing doors, and was proposed to the senior board of H.R.Owen as an Owen-branded model when Chris Humberstone was working for them (briefly) as a car salesman during 1971. He also proposed some other models, which didn't make it to production either, although ultimately H.R Owen did offer the Jaguar-based Sedanca that Humberstone designed.
I have the original drawings for this Saluki, so I will post a scan of the overall design proposal shortly. I hope you enjoyed a 'world debut' puzzle for a car that has never been seen before, and than you all (especially Carnut) for your interesting guesses