Caecilius used his keyboard to write :
I've got a large house with gas central heating which I use during the
day. It gets cold overnight in the bedroom though, so I use a 2KW
electric convection heater with the thermostat set to about 18 C on a
timeclock which switches on between midnight and six am (boiler comes
on again at six).

Could you not arrange a single zone to be on for that bedroom, use a
wireless thermostat and take the thermostat up to bed with you?

I have to ask why your house/bedroom becomes so very cold during the
night? I usually run the general house temperature at 20/21 C and with
no heat input, on a freezing night, my indoor temperature rarely falls
below 19C before next morning.