OK, thanks for that, he actually told us it was impossible for someone to conect to our supply.
We dont have one, what we have is a "Horstmann Radio Telemeter 2A", type NU077-124 with a red flashing led.
If thats the case, then do you think it safe to assume that the led should not flash with everything turned off ?.
Its a digital display, so i can monitor this way.
Theyre almost full, so would probably be OK for 24 hours.
Were going to do it on a night, then pop outside and see if neighbours lighting has gone off :).
The engineer said that he checked for this by his tests anyway, eg he tested with his own kettle the load, and it was pulling the expected load.