The stormy weather led to a power cut here last night and for most of today. Whilst feeling smug that we didn't have damp down the fire (water from stove to tank doesn't require a pump, designed this way in case of power cuts), I had to concede that the heat wasn't circulating from the tank around the house very effectively without the pump. However, the hot water doesn't depend on electricity, as it's just mains water running through a coil in the hot tank. Therefore we could spread the heat around by putting hot water into lidded pots to make temporary radiators.
An extra layer of clothing helped, too.