Iain learned that the plates were London registered: by this list -
A quick look at the dvla site suggests the numbers are no longer on those cars.
Ivan knew that the car company was French, HOTCHKISS. Benjamin Berkeley Hotchkiss.
Tire Van knew that the cars are running on Dunlop triplestud tyres!
Jean-Frederic was the most recent of the correct answers, and that is the list of people who knew what they were and emailed me...
The badge in the grill is easy to identify once you've seen it
thank you all!