I am not qualified to tell you Paul, and I think in this case, opinion isn't good enough. But, one thing that I can tell you is that this is more about the breaker that you fit than it is necessarily about the rating of the fuse. The reason that you need a round plug is that std 3 pin ones can't handle the load. They turn to carbon in the end. But what trips the breaker isn't the working load, it's the spike when you start up. I went through all sorts of MCBs until I got a motor rated unit. D type from memory. It's only 32 amp but it takes that initial higher surge without tripping. Obviously a 200 amp welder doesn't draw 200 amp from the mains.
I would say that if the unit, whatever the output is wired for single not three phase then it will run from your mains with the right connection and set up. Where else would you realistically plug a single phase welder? What I don't know is what your mains is like in terms of wiring etc. That's why you need someone who knows more. But the reason that I mention the MCB is because I have met electricians who can do all the wiring calcs but STILL get the speed of the breaker wrong.
Chris
