Unexplained volt reading from domestic dual rate meter installation

A domestic hot water cylinder was not heating properly on E7 so I popped in early to see what was happening while the economy circuit was live. It's always a good idea for the thermostat to be turned up... tends to heat the water better!

While doing the usual tests at the immersion heater I found this: L-N (230v), L-Pe ... ZERO volts! Dodgy earth? And then N-Pe 230v !! What's this??

I would say the supply is TNCS. I chased through the wiring and found 230 volts across Pe-N in the consumer unit (only part of it reproduced below). I just don't see how that can be possible...?

Sounds like you might have a reversed L - N

I would turn the CU off and check the incomer is connected correctly if it is your next call is to the DNO

On a TNCS supply you would not normally expect full voltage N - PE

Did you test other sockets around the house.  ?

If it REALLY is wired as per your drawing, the connections into the meter are wrong.

From left to right  it is usually  L in, N in, N out, Lout,  Off peak L out

So you have N out going to your L in on the main switch, and (presumably as not drawn) your peak rate L out going to the N in on the main switch.

So no update on this then