Hi Chimp

The Clarke machines from Machine mart are good machines, not too many settings and also will work with 3 pin 13A plug. I actually have one as a back up welder. I would also avoid the dual gas / gas less machines in my experience with friends who have had them they are not always the best for welding.

As Dave said a course will only teach you the basics and you will learn more trial and error by yourself, you will soon learn if the power is set too high or too low very quickly. Most motor factors will sell sheet steel, DIY stores also sell Steel parts just make sure you remove the lacquer before trying to weld it, as this can cause bad welds and give you difficulty in striking the arc in the beginning. 

Lots will say flux core is crap, but it not! it takes more time to clean but can be used outside has its place, If u only weld just a bit each year I would buy one, I used a Clarke 151en for years for small jobs it was good they are 30 - 150amps. and duty cycle of 15% at 130amp it is small can be pickup by one hand ,,Lots will say buy a big 180A , like a snap on? or Sealey Professional?,, but you can not pick them up as too big!!, I have a cobra 180A but the duty cycle is  20%? at 140amp the Sealey Professional is 30 - 180A and 15% at 145A duty cycle    If I was looking to buy new I would look at a R-Tech? all ways best to buy a welder for more and your needs a good welder like a Portamig or R-Tech etc cost more to buy but do sell for good money and parts are call away,,I only got a Clarke as at the time there was not a lot of mig welders to be had new cheap?,,