Hi there.Hi Dougie,
Basics first, the earth clamp is the rubbish one you get with car jump leads, which are useless and get hot in use. This one on Ebay is the type you need, not expensive and you get to see the cable lug joint isn't damaged and a copper connection all the way to the work.
With a minimum current of 60A with the wire feed speed you really need to follow the thin material tutorial and weld with spots as this welder is more likely to burn holes in thin stuff.
You didn't say what you first settings were, but if you get the same result nudging both the controls up gradually till you are running it flat out on 1mm steel I would say you have an excuse to return it and get your money back.
Thanks for your reply. Blimey.. I certainly hope it’s not the machine. I’ve had it since July and practiced on and off but only recently sat down and thought I’d knuckle down and learn properly as there’s some bits I want to do on the car chassis.