The unions were created to fight the exploitation of the workers who were paid low and worked hard for centuries. The demarcation disputes were often cited as being one of the ways the workers were being difficult. In reality these were due to workers asked to do work, other than their specific job, then being injured, or killed, and employers disclaiming liability as they weren't doing the work they were paid to do.
Thatcher set about destroying the unions, the miners in particular. The state was engaged in all manner of unlawful actions in order to do this. The book, "The Enemy Within" by Seamus Milne gives a thorough account of all the dirty tricks used by the police and security services.
My gt grandfather was one of those who formed one of the first railway trade unions. I think he would be sickened by the destruction of the unions which means that people these days are exploited once again. Zero hours contracts, the so called gig economy, short term contracts, there are few permanent jobs with decent conditions these days.
The Tories have returned the work world to favour the rich bosses and companies at the expense of their workers. Look at Amazon, just one of many to have poor working conditions and treating employees badly.
Helig