@nprofile1q... I don't get why UK fuse boards are still the same tiny boxes they were in the 1950s.. but it seems BSI/IET doesn't want to modernise anything in that regard. Especially adding anything "smart" inevitably means adding external boxes around it. I follow a few UK electricians on YT, and always cringe when I see these wooden boards with assorted boxes and wires bolted onto them..

The outgoing cable looks tiny for a 40A circuit.. what does BS specify for that? I assume 3x6mm²?