@KayPnuts has the solution to in-house-display (IHD) only showing gas usage, and the electricity meter not sending its reading to ScottishPower (SP).
It is relativly expensive to send someone out to re-enter the home-area-network (HAN) settings, such as paired devices; compared to getting their customer to send the readings online.
The modem attached to the electricity meter, collects meter reads from the other meters over HAN, the modem sends these readings to SP over the Capita Smart DCC the mobile phone network.
Energy unit prices are sent from SP over DCC network to the modem, the modem sends them to the IHD over HAN.
Meter software updates are sent from DCC, over DCC network to the modem, then to the meters over HAN. Although the electricity meter has a wired data serial port and power connection to the modem.
My in-house-display (IHD) seems to be working on both fuels again
When entering my meter readings online, the suggested readings were almost correct.
Looked at energy usage page, and both electricity and gas were displayable in half-hour units.
Plugged in IHD and power on, initally showing only gas with no electric account details, then the details appeared and the "Now" button works again.