So I got the forge painted, like the original it is very black and difficult to photograph! If it was anything other than a forge I might have been tempted to pick out the lettering in paint but in reality it would never have been.
I did a quick google search for 'vintage belt drive forge blower UK' and found someone selling two on Ebay. I liked the note that said postage was not an option given the weight. Still they helpfully supplied a number of photographs and the key dimensions on their listing.
So the intention is that my forge will be proudly equipped with an Alcosa No4 blower manufactured by William Allday at Paradise St, Birmingham. (Not wishing to offend any Brummies on here but that does sound like a case of Victoria hyperbole to me).
It modeled up quite well in CAD and ends up about 20mm tall.
It's not perfect but I doubt there are many people out there who will be able to tell once it is installed in the gloom next to the forge.