Clive,
I found reference to your carb on the website of Carburettor Hospital, listed as GFD772FKDA. All the entry said was manual choke, ohv, 13/1600. I am taking a stab and saying it may have been for the Ford 1.3 Escort Estate, my memory on staff cars is not that great as I had little to do with them, but I seem to think we had in service, the Mk2 which was petrol, that could have been around the late 70's/ early 80's. Perhaps that narrows it down for your EMER search.
FMW built little warehouse tugs, for ordnance depots, etc, think they were made in Dorset, I recollect the later ones with the awful Transit diesel, but not the petrol model.