There's lots of images and even videos of Triumph and BSA, but none I can find of Matchless/AJS. Of course Triumph and BSA both were much larger operations, and made a lot more bikes and more importantly revenue and profit than Matchless/AJS, but hopefully there are some images out there.
"Of course Triumph and BSA both were much larger operations "
These words will come back to haunt you ? - AMC were at some stage the worlds largest manufacturer of motorcycles. In the early 1950s when AMC was AJS, Matchless, Norton, James, Francis Barnett and a couple of others. Manufacturing was not just at Plumstead then though...
Lets not forget there was a large recession, in the motorcycle industry too, in the mid 1950s, and afterwards the Triumph BSA empire emerged as the biggest. For a while.
There are lots of Plumstead factory pics, if you hunt around. Yodel if you can't readily find any. As mentioned above, the factory was demolished and a housing estate built there.
No images, but I read that Boy George (George O'Dowd)'s father worked at the Matchless in London. I enjoy looking at photos of the factories and workers at much as pictures of the bikes, so thank you for posting. If I was young and had any money I'd immediately buy a 600 twin Matchbox engine and frame, and build a road-going G45 "replica". I think it's one of the great beauties of motorcyling.