Wowsers! My opinion would be to scrap it. Sorry. But even getting a welder, discs, pads, metal plate etc etc is going to be £300-400 at least. Plus cost of another mot (doing all that work in 2 weeks is ambitious, it would take me longer than that to learn to weld!). Then, when you've done that, all you've bought yourself is 12 months. Cause you can bet your a$$ she'll fail again next year.
People are struggling to shift half decent omegas for £500, say you get £50 in scrap for yours (or keep for spares if you have space) and you're pretty much at the value of a different mig. Oh and you've saved yourself hours (days maybe) of agro.
In short, scrap it, but one with an mot.