Only have electric heating in my house which is about 40 years old.
Night storage heaters upstairs. Underfloor heating downstairs. Wires
buried in concrete screed about 6 inches down. Thermostats for each
room - bimetallic strip type ? We kept to Manweb off-peak tariff D when
we bought the house 20 years ago. Seperate meter and supply to heating
circuits. Power from 1 am to 8 am and one hour in the afternoon.

Tiles in kitchen cracking up. We had them replaced. Screed underneath
in poor condition. We ripped it out along with wiring. New screed and
under tile heating arranged by kitchen installer. Can't run the system
on off-peak electricity as the time clock/thermostat/controller chip
requires power all the time and I think the same holds for the RCD. The
controller only has one set of input terminals so we cannot powere the
clock/chip from a 24 hour supply and use it to control an off peak
heatig circuit.

Is there any way to run the under tile heating on the off-peak ? The
concrete floor is not insulated and may thus have some heat storage.
Should we go Economy-7 and put time clocks on all the heaters ?