I wouldn’t bother with the flux wire no gas stuff, it’s crap and you won’t be happy with using it or the results.
the welder I bought came with a 13 amp plug but I got fed up with having to reset the circuit breaker just as I was about to start. I ended up fitting a 16 amp blue plug and using it on my air compressor circuit. Depending on how sensitive your existing 13 amp electrics are, you may find even a 13 amp machine could trip the breaker.
when I got my air compressor (16 amp single phase) I got an electrician to connect in a short spur from the fuze box to a socket about 60cm away on the outside of the house. I then made up an extension lead (armoured) and ran this under my block paving to my electric meter box. When I want to use the 16 amp circuit, I open the box, get the plug out and connect it to the socket about 60cm above that.
all in cost was about £200 8 years ago and I think it’s saved me getting stressed with tripped CBs every few minutes.