The Mig Welder I have is a Clarke 160E Gasless although I would prefer to use it with gas in this instance, most likely Hobbyweld 5, I find the gasless very messy to use.
What size wire should I be looking at, 0.6mm or 0.8mm or is this more a what your comfortable with type thing? I've got some cheap 0.6 here somewhere but I'm happy to buy some decent Esab or Lincoln wire in both sizes as I have a lot of welding on different thicknesses to do in this Land Rover.