Dajwid,
Have a look on here:
http://www.mig-welding.co.uk/Stick's not much good for bodywork. And converting to tig will cost a bit when you think about cost of torch, tungstens, filler rod and shield gas. Also bit trickier to learn than Mig since it's most like gas welding.
Mig still the Daddy for DIY and many professionals too.
Clarke 151TE seems to be one of the more popular budget models. Don't fall for the models that use gassless - again pretty much useless for thin work. And defo dont get a SIP!
If you want impartial advice, try the forum on the link. Lots of info on stick, tig and mig on there
James