Understanding the electricity supply to my house...

[Taylortwocities]

Brief replies sorry ( in a rush)

C: it’s fine. No point calling the DNO, they won’t come out for something like that.

D: you do NOT want trip protection there, unless it is a specific type (time-delayed RCD). Otherwise a earth fault on one of the other consumer units will trip the whole supply, and you do not want that!

General, you should turn your energies/concern to the size of the feed out cables from the meter. They are wowefully undersized for a TNC-S supply. The main earth cables are also undersized.
Also you should look at replacing your consumer units with ones that have RCD protection for the distribution circuits. An RCBO for each circuit is the best (but expensive) solution.

 

[securespark]

It looks to me like the upper one is supplying power to the lower one, which is pointless.

The tails may be piggybacked.

 

[Taylortwocities]

Indeed, also not the best idea!

 

[aptsys]

It would be 'fine' over that distance though, as evidenced by the lack of any degradation. The power dissipation will be minimal.

 

[Taylortwocities]

Maybe. We haven’t seen what is under the cover of the first sw/fuse.