The demise of the British industry was bigger that just the motor industry. Very great social problems beset Britain at that time. Radical unionism was just a sympton of those problems.
Unions were destructive and a nuisance before the war, but the real problems started when anyone worth his salt went off to fight and the factories were left with radical, far left extremists, pacifists, you name it. They even refused to train women and struck endlessly and they owned the Labour Party. They were trying to sabotage the war effort and they nearly succeeded. Worse than that, they were what returning troops had to work with.
In simple terms manufacturing only succeeds by reducing costs to remain competitive and the unions only exist to undermine this every which way. By the sixties two industrial leaders were hired to sort out BL/BMC and both told Harold Wilson that half of the 80,000 work force would have to be sacked to save the company. Because of union intransigence, twice as many worked for the company as were needed. Wilson refused to allow a single redundancy knowing that the problems would affect his successors, mostly Margaret Thatcher because, by the time she was elected, demand had evaporated and there was nothing to save.
There is evidence to show that the KGB were sending "shop stewards" to the UK to help our glorious workers in their struggle, I had friends in Special Branch who had to follow them. At it's core the Unions believed that total collapse of the British economy would result in a Socialist utopia, presumably with them in control. We got to 26% inflation and we were nearly bankrupted by the IMF thanks to all this.
Harold Wilson made speeches about the "white heat of technology" while simultaneously signing our manufacturing industry's death warrant. Eventually he had a complete breakdown that was covered up at the time. Callaghan, his successor had holidayed with Stalin when he was younger an returned enthused by his marvellous interpretation of socialism. Barmy or what!
Britain had a malign influence after the war that the Germans were lucky to avoid. They started anew and we carried in a beleaguered and near bankrupt state, underfunded and against the odds and this left us weak and unable to deal with it. The unions ownership of the labour party left them powerless to cope. Sadly our Labour Party is still union owned, but the Public sector now.
When it was too late, many of those in coal or manufacturing realised that the unions had robbed them of the life they loved and that they'd just been a pawn in power game.
Social problems, not really. Dirty politics more like.