Not sure about the Raglans, the 280 looks identical in many ways to the Harrison M300, same bed casting, same saddle, same headstock casting but the two speed change levers are mounted on top of the Myford but are still basically the same inside the box. The apron and the screw cutting box are different but elsewhere the similarities seem never ending!
It seems no one knows anything about their manufacturer but I’ve seen so few out in the wild I wonder if they ever produced them in any reasonable quantity. Someone must know something, I’d assumed they were made in nottingham but never seen any photos of the production, whereas there are many pics and history of the rest of the range. I’d be surprised if they weren’t made by Harrison.