I still have a few of those GEC light switches in my box (pic #2 top/middle and pic #3), although they're a little cleaner!
I'd put the MK sockets at early/mid 1950s, which is consistent with the rubber-insulated cables. The BS1363 standard didn't appear until the very end of the 1940s, so there weren't many British homes which had these sockets before about 1950 at the earliest.
