i have a sealey 150super MiG. its a good budget welder, but if you want smooth runs every time and a welder that can weld 10mm plate without over heating i wouldn't bother with one. you should always weld with gas, i believe its the law when it comes to auto repare. i use 0.8mm wire you can get .6 but that's like welding with fishing wire and not that good really. if you want a cheap one get a sealey, all the parts are available from the UK and there pretty quick when it comes to sending it out, if you were to invest in a goooooood one get a migatronic, Lincoln or a kemppi, have used them all and rate them very highly.
Clarke is another alternative for the cheap option but i don't think much of them. i think if you get yourself one like mine you'll be fine :D
my two pennies worth
hope that helped
Boss