In Hayes Middlesex England just north of Heathrow Airport as you come over the railway bridge there is a small industrial estate on the left. I was told years ago there used to be a “bullet factory” there during the war.
I suspect it was Kynoch’s K4 Yeading although the village of Yeading was about a mile further north.
In the interests of local history I am trying to document it. Has anyone got an address?