On Tuesday, 19 December 2017 17:44:05 UTC, Steve Poulton wrote:
Please help. I have a basic understanding of electirics, but 5 Electricians
are stumped and I don't know where to go next.
for full context, visit https://www.homeownershub.com/uk-diy...t-1257719-.htm

There's even more context at

https://www.electriciansforums.co.uk...ircuit.124737/

So far possibilities seem to be (a) a polarity error as I suggested - possibly introduced due to a meter change - or old 15A MCBs overheating and thermal tripping.

Owain