The difference in trades is that they will always have a demand because people will need plumbers, contractors, electricians, welders etc.

Really? All those people working in Robotics just stopped today, did they? So, we can get cars to drive from one side of the United States to the other with no driver but apparently plumbing is just impossible for a machine to recreate?

The way technology is going currently, the assumption that any job on Earth is safe is moronic. Especially manual ones that follow a process like electrician, plumber, welder.

Whereas the rate of University degrees is so inflated and so many graduates don't even find a job related to their field.

This completely depends on the field, though. Actuarial Science, Pharmachem, Electronic Engineering, Computer Science, Accountancy and a good few others are desperate for graduates. I'm not saying go to university for shits and giggles, but make an intelligent decision. You also have to consider having a degree in something like Computer Science makes it a lot easier to rotate to something like Engineering or Business Analyst than being a welder will ever give you.

Then students will have to spend an extra year or two in grad school to earn their Masters or doctoral while the debt piles up.

This is just an unfortunate American issue. Completely the fault of the average American but I understand some people just can't afford the debt so I sympathise on that one. My advice applies mainly to any Western country that isn't the United States.

Maybe it's different in Britain where it seems you're probably from.

Republic of Ireland. Them's fighting words, lad.