As for the coal industry, the National Coal Board (NCB) had been closing pits rapidly since its inception in 1947. When output was at its peak between 1913-1920, there were 1 250 000 men and boys working underground, and when you factor in the people working overground and all the related industries, something like 4% of Britain's entire workforce was related to coal. Britain also mind 25% of the world's total coal, and was responsible for 55% of coal exports at this time too. Many of the pits then still had coal gotten by hand with picks, haulage relied on pit ponies and self-acting inclines, and flame safety lamps used instead of electric ones.
By 1947, that number was down to ~750 000, largely due to increased mechanization (electric coal cutters/longwall shearers, hydraulic props, diesel and electric locomotive haulage), and private operators closing money-losing pits.
The biggest job losses in the pits came between 1960 and 1970, falling from ~700k to ~290k. It wasn't just a matter of "rule by shop stewards", and NUM (National Union of Mineworkers, represented miners and colliery staff) and NACODS (National Association of Colliery Overmen, Deputies and Shotfirers; represented officials) labour being expensive, but because foreign coal became cheaper. British Railways was also dieselising, coal-fired ships were being scrapped, and home heating was switching to gas, oil, electric or to smokeless fuels instead of open coal fireplaces. Mining attracted far fewer people because the pay became below average with 1970s inflation.
In Victorian times, when coal mining was poorly regulated, and over 1000 men and boys each year lost to devastating explosions, there was never a shortage of coal miners. Why? At that time, the average factory worker made 1 shilling a day. A mine haulier or shifter (labourer) could make 2s a day, and a miner actually getting the coal could make 2s/6d - 2 1/2 what a factory worker did. Colliers also got a customary benefit- all the free small coal (coal that was in pieces too small to sell) he could carry, and a "tied cottage"- typically a 1 1/2 storey dwelling that was free or had massively subsidized rent. There was also a path to advancement- typically, in a coal mine, the officials (above the miners but below management and spent the day underground) were promoted from "practical miners". Shotfirers (responsible for explosives) made a bonus; deputies, master shifters and master hauliers made a higher salary, and overmen (the most senior underground officials, responsible for safety and production) made even more than that- often more in a day than a factory worker in a week.
By the 1970s, the NCB is bleeding miners. It doesn't pay well. The excellent apprenticeship program has young men signing up, staying the minimum 4 years in the pits, and leaving. I saw an old interview with a Yorkshire miner in the 1970s. It went something like this:
Interviewer: Have you always been a miner?
Miner: Aye. And me dad, abd granddad,and great-granddad.
I: Are you proud to be a miner?
M: I were proud. Not anymore. They don't pay you what you're worth, and it'll never be safe like overground work is. Every day you could just as easily not come home.
I: You have a son?
M: Aye, I do. He's in school now and I forbid him to leave like I did.
I: What if he told you he wanted to go down the pits?
M: I'd break his legs.
Even without Maggie on the right, and militant Marxist NUM President Arthur Scargill on the left, the coal industry is on the brink, and it's going to fall on someone.
A gross oversimplification, but if coal fetches £40/ton on the market but costs £120/ton to mine, and most of the best deposits are depleted, how long can you go on?