According to https://vehicleenquiry.service.gov.uk/ViewVehicle it's a Morris, first registered in june 1968.
It's also one of my favourite vintage trucks. Growing up in the 1960s, I got obsessed with cars from a very early age. Especially ones that had some sort of unique features, like the curved floor window on the FG.
Nowadays, as a model collector, I've also found it to be one of the most badly neglected trucks. Despite the prototype existing as both Austin, Morris and Leyland it's almost completely ignored by model makers.
A few 1/76th scale models exist from Base Toys, and there's a fair to reasonable 1/43th scale model sold in the far east, but not imported to Europe at all. I've been very tempted to buy one, but expect the import duties to be extremely high.
Wikipedia is not much better, as information there is very sketchy, so I guess my passion for this truck isn't shared by many others... unfortunately.