Chewing The Fat..... "Volt-Drop"...

[UNG]

Out of interest, was there a lot of PV in the immediate area?
I had similar, and my suspicion was that in this upper class residential area a lot of early PV adopters without battery storage and lack of daytime loads was pushing the supply voltage up. I couldn’t prove it though.

You have guessed correctly
Seems to be the norm these days and it is becoming more difficult to avoid the inverter dropping out due to the high grid voltages although it could be good for selling battery storage

 

[UNG]

Having thought about the OP's conundrum there is a solution to the volt drop issue given on the EIC where there is the option to note "Departures from BS7671" if you can justify the reasoning for adopting a higher volt drop then the problem is technically solved, some may not see it as an ideal solution but as long as it can be deemed safe and does not present a danger I think it offers a solution to a common problem that occurs quite frequently
The only problem that may appear later on is when Mr DIY wants to add sockets or a heater and carries on regardless of the limitations of the installed supply