Thank you gentlemen. Buying a MIG welder and teaching myself to use it is my preferred option. What was the welder you recommended recently, Nick? Is it reasonable to buy a welder, read the instructions that come with it, and teach myself how to do it, or do I need a college course?
That's how I did it, but I had been using a stick welder before. Even with that experience, lots of practice was necessary before I considered welding the car.
A college course isn't necessary, but half an hours instruction from somebody who knows what they're doing will considerably reduce your learning curve. You will need to buy a sheet the same thickness as the car; buying thicker than that is a waste of time and money as you will still need to practice on the correct size. If you can get it sheared into 6"(ish) squares do so.
What else do you have in the way of tools? You won't do any electric welding without an angle grinder and an assortment of cutting/sanding discs. You MUST use PPE; a proper welding mask, gloves, safety goggles, and thick cotton overalls are required, and a good large fire extinguisher is a damn good idea. Using the disposable gas cylinders is expensive, and they don't make for very good welds; a proper cylinder and regulator is likely to cost another £150.
My welder is a semi-industrial machine, and would cost over a grand to replace so I can't really advise on a machine. I would be looking at buying an inverter based machine if I had to buy a new welder.
Realistically, you're looking at spending £500 before you put a torch anywhere near a car. Unless you're expecting to use the tools a lot, I would suggest that's not good value. The <<£200 machines
will do what you need, but not in a beginner's hands.