I guess there's a bit of info here for everybody.....
If the pieces to be welded are easilly accesible then TIG everytime for me, it's so much neater and cleaner. If however you're upside down then TIG really isn't practical and a decent fan assisted MIG will be perfect. I've also got a Clark 135TE Turbo which has done me very well over the last 5 years or so. I seem to remember the instructions saying it will weld (penetrate) 6mm mild steel, i found it could just about manage 3.5 - 4.0. Any thicker and you have to taper the edges. Still plenty good enough for any car work. this cost me £200, i've noticed they've put the prices up. It's been very reliable and has put up with a lot of abuse like being dropped. it's got wheels on it too which helps when draggin it around
My TIG set is unfortunatley scratch start, the HF version was about £650. Its one of these invert-R jobs and i got mine with TIG torch, three tungsten tips, three different size collets, regulator for a larger gas bottle, mask which i threw away, how can you hold the mask and the torch and use filler rod at the same time???. Bought a auto darkening one instead, well reccomended, earth electrode and arc rod clamp for £250. i thought that was a bargain especially as it was new. Mine drops down to about 20A and goes up to 120A if you want to switch the cables and use it for arc welding. its also small enough to wear over your shoulder which i have found to be handy for a few jobs.
Just from experience, if you do all your welding outside and are not sheltered then gasless is the way to go, i've found the welds to be less neat than with gas but a lot neater than using a gas set on a windy day! Oh and a gasless set is a lot cheaper too in the long run, having to re-do welds which have had the gas blown away can get expensive if you're using the disposable bottles.
I'm not sure i'd spend £100 on a second hand welder though, i'd rather put that towards a new one with a warrenty. but that's just me!
Appologies for the waffle[:p]


