As an interesting comparison, maybe you've seen it before, a visit to the present day BSA factory: https://www.youtube.com/watch?v=jhm1HnJkDfQ

Apart from the barrels there doesn't seem to be any other fabrication there - I can't see any sign of it anyway like lathes & milling machines in the background, I think they are just assembling components, presumably from Gamo in Spain. Very sad when you see what it was like at one time.

Still, it's not often you will see a war time period unissued SMLE though - & the machine for making Meteors, looking a bit unused & forlorn...