Ah, sorry I hadn't even considered that it would be different in other places (just times) - I'm in the US, and those flat ones were present here at least as late as the 1980s and likely 1990s.

Cable Internet is very common in the US, in fact the most common kind. (2nd is DSL) So the F connectors (didn't know that name) are everywhere. Also still used for actual antenna connections.
I am not sure if I have ever seen a Belling-Lee, but RCA used to be extremely common here until HDMI took over that role. (In fact RCA is what is on the switch box above to connect to the 'computer')