What's more economical?

[coccinelle]

I have gas central heating (propane) with no central thermostat, (however there are some radiators with thermostat taps on them). My bathroom radiator can either run off the central heating or the electricity, this radiator doesn't have a thermostat for the central heating.
I only need the bathroom warm in the morning for my shower etc
My question is; which is cheaper? Opening the radiator the night before (on central heating circuit) for it to be warm following morning OR to programme it to come on the electricity one hour before I need it?
I have no idea how to calculate this....

[The Builder]

If your CH is on anyway, Cocci, I would open the valve on the bathroom rad. In fact, I wouldn't close it for the winter. Better to have a TRV (Thermostatic Rad Valve) fitted, if possible.
Failing that.......... ( I guess you're worried about the cost of an uncontrolled rad steaming away in the bathroom all night?) ............... leave the bathroom door open. Excess heat in the bathroom (won't be much ..... towelrail?) can then escape where it will help to keep the other, controlled, rads working a bit less.......... no waste then.

[coccinelle]

Thank you The Builder. Yes, it is a towel rail but quite a big one for the size of the bathroom. You're probably right in leaving door open to help heat other parts of the house (the corridor and WC aren't heated) and I will shut door half an hour before using bathroom. Not quite sure about leaving the bathroom radiator on all winter though....