I'm also predicting this one, which was the final reason for the panel heater in the bedroom and not fitting the second heater in the lounge. At the moment that property is on 18.71p/6.84p which is a little over 2.5:1I've just noticed this one.
I think you may be rather out-of-date. Until around 3 years ago, tariffs with day/night ratios of around 3:1 were not unusual. However, today on has to look quite hard to find even 1.5:1.
As nocturnal EV charging (hence nocturnal demand) increases, one imagines that the ratio will eventually 'flip' to the situation in which daytime electricity becomes cheaper - which has the potential to throw a spanner into the works of the storage heater market!
Kind Regards, John