What you're looking for is a welder that goes down to (ideally) 30 amps or less and also one with a reasonable quality wire feed unit to give trouble-free operation.
The worst thing you can do is buy a welder on price alone, you're almost guaranteed to get some sort of trouble with it and getting spares for lesser known brands can also be a problem.
What sort of budget do you have and are you looking at new or used machines?
Sorry to say but at that price, none.
Even an entry-level Clarke Pro90 will set you back £200 for the machine alone, factor in wire, gas, gloves, decent mask etc and you've blown your budget well and truly out of the water.
If you purely want it for bodywork and will never need to weld anything thicker then the pro90 would be ok. They're by no means professional quality but they're good, reliable machines and being Clarke they have good spares and consumables availability.
Avoid anything by SIP or cosmo, siegen aren't too well regarded either though red-cased Sealey ones don't seem to have a bad reputation on here.
Avoid anything on Ebay that appears too cheap to be true, they're cheap chinese imports and, well....say no more!
If you think you may 'grow out of' the machine and decide you want to weld thicker stuff then something like the Clarke 160TM is a nice machine.