I'm impressed, there seem to be some really good welders round these parts.
I'm another one who got a MIG setup for car repairs, but always struggled with the the welds on the thin bodywork. I got a basic TIG setup, which was a lot better in a lot of ways. But a. very slow, b. required a lot more cleaning of the metal than sticking it on with a MIG gun and c. is a lot trickier working underneath these things.
However I have done some reading and it turns out that the frustrations I have with MIG work seem to be common to the machine I started out with. Despite really stretching myself to get something better than the DIY models from Machine Mart, the range I bought from seems to be flawed. I've recently bought a smaller DIY machine from Machine Mart and I'm already getting a lot better.
I've never managed to do very good welds with a stick machine, but I very rarely work on anything that thick. My main problem is not welding often enough to keep in practice - it feels like I need to re-learn everytime I come to a welding job.
I did an NVQ evening class at a local college around 15 years ago. Welds aren't pretty all the time but as above I don't do it often so don't keep the practice up. Have an arc from Lidl and a Sealey gasless mig. Do the job for most projects that I need to do.
