Are those figures all typos (i.e 100V less than they ought to be)? If not, I'm confused - since 141V - 143V is somewhat on the low side .Later that night, I measured the voltage at the new socket. I got between 141-142V L-N & L-E and zero N-E. I took 3 or 4 readings and each time got the above readings. I repeated it 10 minutes later and got 143 V and again, zero N-E. ... I've used the socket a few times since then (wouldn't use it until I'd tested) without incident so I'm confident everything is OK.
... and I'm sorry to hear about your experiences with the electrician, but glad that you more-or-less won in the end! He sounds like a close relative of some tradesmen I have encountered in my time
Kind Regards, John