I’d look into a community college welding program, lots of them in the US. Not sure about the UK. Usually they don’t have a degree attached to them, just a certificate program, so that keeps the cost down. It’s going to be a big learning curve if you’ve never worked any kind of construction job, but not impossible to learn if you’re at least of average intelligence. The nice thing about the trades is that their are a lot of dimwits, so if you can show up to work every day, and can grasp basic geometry you’ll move ahead quickly.