One tip, avoid the Clarke 150TE unless your willing to wire in the welder to a 20amp fused isolator switch, this is what I have found out this evening. I have though asked the question over on the mig-welding forum pages if It's possible to fit a robust 13amp plug to the welder If I'm not able to change it for one that can use a standard 13a plug, and the answer is yes as long as the welder setting is not on max!
Have you tried to fit a 16amp plug and then use a stand alone 16amp rcb?? i had to do this with my compressor as the 13amp rcb kept tripping.
I've not heard of folks having problems with the 150 before but then again when i bought my compressor that came with a manual stating all i would need was a standard 13amp socket and power supply. How wrong was that.
In my new house i will be fitting a stand alone 25 amp power supply for my compressor so at least if i decide to go up in power for a new Mig then i can use that so as not to fall foul of your problem.