A bit on Leyland. First problem was selling the mini for less than it cost to make. They weren't the only ones to do that and may be exaggerated so say not enough profit especially for completely new models so turned out what were called kit cars by some - chassis & floorpan say from an existing model plus a new body and that sort of thing.
The assembly line was often in the news. I have known people who worked on it and plenty of other people who knew some one as well. There was absolutely no way anyone could earn as much as the papers and tv claimed - no where near it. Problems came over pay. Traditionally they only worked when cars were needed and laid off when not. Sales are very seasonal. So eventually unions negotiated a deal where they were paid all year round cars needed or not. This is where Red Robo comes in. Very easy to do something that will cause a strike. So don't want any cars easy create one - no laid off pay outgoings then.
I actually worked in a place that did the same thing. Come August a strike would always be used for a pay round negotiation. They never lasted for long and the people who did it where the ones that kept the factory equipment working. Bright new general manager. High level director just below the main board. He ran the factory flat out for several months in preparation and filled the warehouses. Pay round came up and he just refused to talk to them so not settled for months and months. Settled when stock ran down. Settled for what it probably would have been anyway. General manager tells main board - well if all had been sold there would have been a small profit. Being staff and not works I worked all of the way through it. Many didn't.
Another place I worked at in the same group. Door open so walked into the general managers office. He was on the phone which had a second headphone and his number one was listening in. After they had finished I asked what it was about. Being told how to cause trouble with his workforce.
He didn't want any. A lot of this sort of thing was going on. Strikes were wanted and not by the company who hardly ever had any. Usually just short ones by the lot known as works engineers - they fix and wire the kit used to make stuff. Production stops as soon as something breaks if they are out.
One of my very early jobs was moulding in Made In Great Britain on a number of products. Several months later removing it. Many things went to Taiwan eventually. This was before the time when Made In Great Britain might be put on some small part of something or the other that was mostly made elsewhere.
Way before there were many about I was given the job of looking at as many foriegn cars as possible to see what battery etc they were fitted with. At that time it was extremely unusual to see any foreign cars on our roads at all.
Then Mrs T made it far easier for investments to go elsewhere. Did she have to do what she did in this area - yes. Did she have to bash unions so hard. Probably not and it's left things too lop sided so people tend to get inflationary pay rises that long term depress their real income and there are far more things to buy. Answer pass. Wilson legislated the pay rise one year. It lead to an explosion in share deals and company cars. Now we have the minimum wage - an idea the Tory lot hated when it was introduced but is a form of control.
What happened to manufacture in general is another story.