Mike G wrote:

Interestingly, the Clarke 120E MIG I had before never once cut out,
despite not having a fan fitted.

You should have kept it. :-)
My 120E gets used a lot. AFAIR I baught it in the late 80's. It's never
cutout, and apart from replacing the nozzles 2 or 3 times, has been
completely trouble free.

Yup, mine was the same. I replaced the tube liner once when wire feed
had become a bit uneven, and discovered that running large reels of wire
instead of the little ones made the feed much smoother, but otherwise
had no complaints. But then I was offered the SIP at a price I couldn't
refuse so flogged the Clarke to a mate.
The SIP was a revelation! Immediately the quality of my welding (which
previously I'd been happy with) improved more than I'd have believed
possible. I'd been sceptical before when people on this group went on
about how much better professional grade welders were, but I'm afraid
it's quite true.
Or would be if the damned thing still worked!