I am not sure of the National situation, but, locally (I live in a Colliery "village", although, I never worked in the Coal Mines) the Coal Mine closed 40 years ago. The site of the former colliery is now called "Colliery Wood" and has mature trees growing there.
If we assume a Coal Miner who was 18 at the time of closure, that person would now be 58. Although I never worked in the Coal Mines, several of my Cousins and various other acquaintances did, the only two who I can think of, who are still alive, are aged 86 and 94.
Opencast coal extraction is still going on, to the best of my knowledge.
Interestingly, it was a school trip to a Coal Mine (Westoe Colliery) which perked up my O-level results. We were taken down the mine, and, actually right up to the coal face, where coal was being extracted with the aid of a huge and incredibly noisy machine. I am sure what we saw was the "good" bit, I doubt the NCB wished to kill off a few schoolboys. However, that visit (around 1962) was enough to convince me that I never ever wanted to actually work down there. Since I had already decided that woking in the Ship Yards was not for me (my father was a shipyard worker), I had no choice but to get myself a few O-Levels and get myself a "cushy office job" 😂