More than likely the main earthing conductors will be separate and each flat will probably have its own TN-CS supply where the main earth is taken from the neutral at the cutout. The neutrals will be linked together but that would be at the main transformer so could be some distance away.

Each dwelling should be electrically separated from each other too, even main equipotential bonding will be separate for each flat and if the supplied services are in plastic there will be no link between flats.

even earthing is likely to be seperate, but depending on the building arrangement, may fall back to a common earth point.

Electrically, they will be isolated, fed from a seperate REC

Even the earthing? I thought that the power plugs worked over earth, although I don't know anything about it so could be completely made up.

Should be separated so they can be accurately billed. Don't think that falls under regs, but standard practise.

Every flat I've lived in has been isolated from the others. The power has come from a distribution room where the meters are and then up to the flat. Current place is slightly different because it's so big; the distribution and meters seems to be on a floor by floor basis as it looks like the meters are at the end of the corridor.

Does someone know an actual answer to this, not maybe.

Is there some standard in place that requires flats to be electrically separated?

Reason for the question is these network over power line plugs.

Just tried to use one in a flat, directly next door to another flat but there doesn't seem to be a connection between them.

It was literally one on one side of the wall and one on the other.