I teed the bathroom towel radiator off the gas boiler circuit that heats the hot water cylinder. As others have pointed out, peak rate electricity is ruinously expensive.
That's fine if you have a hot water tank.
If its a combi you'd need to turn everything off or heat the house..
Granted leccy is costly but a good option for some situations.
All the apartments at work have leccy towel rails and it doesn't seem too bad.
There water filled and can be on for an hr or all night.
300w element so like a multi bulb room being lit for a few hrs.
But i guess its all down to the personal situation.
It would be a leccy one for me if we have one.