but the Uk is always going to have a workforce including lesser or uneducated people (not everyone can get a degree)
Firstly the idea that people need degrees is a rather sad disease in modern culture.
We give people 13 or so years of free education, yet this is producing vast numbers of people with no useful industrial skills, that is a big issue.
isn't it better to keep these people employed, even if the government had to subsidise manufacturing
As you point out, we do this for agriculture.
And we have a very large deficit. And we have recently had people complaining about the large scale abuse of these subsidies.
Subsidising manufacturing to the point of employing an extra 500k+ people, would be a major economic drag to the rest of the economy.
The problem with subsidising "anything" is that the successful productive parts of the economy have to pay for it, making them less successful and productive.
I'm not saying we should just stuff the "uneducated" and low skilled workers, but throwing more money at it is what we have been doing, hows that worked for us so far?
The problem as I see it is a failing education system, it has produced a "lost generation", this is a whole other discussion however.