Socket/ switch heights

[swaRRR]

I think you're overthrowing it.

But on an extension I'd put them the same height as the rest of the property.

Yes always match what's there.

I don't like 450mm anyway, i think it's much too high.

 

[mainline]

Off plans, heights are usually specified off FFL… finished floor level… so there should be someone on site knows where to measure from.
Applies to new builds.
As above, if there are existing switches and sockets, you can put the same height…. As long as it’s not skirting board height from 100 years ago.

Nothing wrong with skirting board height switches, it means someone with no arms can kick them on.