[Willem Fick]

I say yes too. (Here in South Africa we also are on the UK standard of 220/230V @ 50Hz)

A normal UK plug has three prongs. One at 0V (neutral), one at ~220/230V (live), and the other being earth (sometimes called ground). What you are proposing is to couple your welder to an output that consists of a +110V side a -110V side (two separate phases tapped from the same 3 phase city supply, hence out of phase to one-another), and an earth. The potential across your neutral and live wires is still 220/230V in this configuration.

This is in any case very easy to confirm. Simply hook up a multimeter set to AC across the live/neutral pair from the socket you intend using. It will read anywhere between 210 and 250VAC, and thgis is the only important consideration here.

Oh yes, your neutral is never connected to earth, as this will most definitely trip your breaker whether the device is switched on or not. The reason for this is that neutral and live actually take turns at being live due to the fact that you are dealing with AC. Convention dictates that the side identified as live (red/brown in the UK) is always switched, whereas the neutral side (black/blue in the UK) is continuous.