You can get individually fused sockets
If you were to run a trailing socket with a fused plug (like an adaptor lead) it should be fine, but I wouldn't like to hardwire a non-NF marked socket... Just think from an insurance company perspective.
Depending how long you want and the rating of your machine(s) you might find 2.5mm to be undersize.
What circuit protection do you have?
As over hear when useing ceeform plugs sockets, witch is common place for welders, plasma's there is no fuse. Just use the circuit protection at the beginning of the circuit.
Live and neutral are treated the same everywhere in France.
I have seem to have a good steady supply at 220 but this can change over the winter period due to our location and the inevitable power cuts.
Plenty of fused 16amp choices in the barn to get me going until I sort out an appropriate extension lead.
Paul, the times they have a changed... If you have a consuel inspection (now mandatory for new connections to the grid in France), one of the tests is to measure the impedance of the earth and this is done by the inspector on the day.
As your on triphase, have you considered if you have the overhead in your supply to run a single phase plasma the same time as your compressor and the household water heater ballon?
When I was on a 20a/phase tarrif, I couldn't run my compressor and plasma at the same time without popping out the disjoncter. I used to hear the compressor chop in and have to stop cutting until it got back up to pressure and turned off.