After much playing around with different fonts, these are the ones which may suit. The military directions regarding font size and type are making it VERY hard to keep this historically accurate. When using the correct height and width of font for the unit numbers, it fills the entire plate, leaving bugger all space either side. And thats with a font that is still a little smaller than specified. This problem is due in no small part to the signage I need for my Fathers unit, 29-46 Inf Btn.
It's a bit like 'Goldilocks'

This one's too small.....

This one's too big....

This 'bastardised' version, while not entirely following the regulations, does match two similar plates I have seen in original photos where the unit had a lot of numbers to fit on the plate. So I guess this one could be......Just Right

Maybe. I'm over it for now

On a happier note, this mock-up of the PASS side of the plate looks just about right compared to the drawings as shown in military regulations documents.
Once I settle on my requirements, I will take the 'mock-ups' to sign cutting place on Monday afternoon. They will probably tell me "Oh no sir, we don't have any of those fonts. At which point I will strike them roughly.....and run away laughing insanely