Manufacturing has been going up year on year, but now only employs approx 350 thousand people.
When we are only employing 350k people in total, we are never, ever going to employ the 2.5 million people on the dole in manufacturing jobs, unless we get rid of the minimum wage, require that people move to where the jobs are, relax employment laws, and lower national insurance and corporation tax (remember that with national insurance your employer also has to pay a larger amount than you do in your wage).
We may not employ such large numbers again, At its peak Vauxhall in Ellesmere Port employed about !3,000 people (don't quote me on exact figures) In those days a lot of things were assembled on site, engines gearboxes etc. Nowadays cars are built using a lot of sub-assemblies some built in other parts of the Uk, some imported.
Vauxhall now employ about 2,100 people at Ellesmere port, There is a supplier park (industrial estate) where companies supply components etc built close to the site, other suppliers in Deeside and surrounding areas. There are also all the sub contractors, builders electricians maintenance etc etc etc ( I know an electrician whose company went to do a 6 week job there, all went well and they got ongoing work on site he worked there for over 20 years)
So although not employed directly by Vauxhall in producing cars many other jobs would be affected by its closure. (there is/was a local company who just fitted tyres to wheels and deliver them to the production line as required, would they technically be counted as manufactures)
Having a "big factory" in the local area is a big benefit to the local area, and local shops etc. I'm not sure what the wages / salary are like these days but they were always above average for the local area and a lot is spent in the local area, helping the local economy.
You also mention in one of your other posts about the UK manufacturing high tech goods with "educated" workforce, but the Uk is always going to have a workforce including lesser or uneducated people (not everyone can get a degree) isn't it better to keep these people employed, even if the government had to subsidise manufacturing, (they've been doing it with agriculture for years) surely better to subsidise their employment than pay them a larger sum in benefits when they are all out of work.
If we as a country are only going to find employment for the "better educated" aren't we going to achieve a situation where the "educated" are paying taxes to fund benefits for the "uneducated"