I would imagine that the property will already have a meter installed set up for the economy 7 tariff......basically you will get 7 hours of nightime at a much lower rate than the daytime.
The storage heaters themselves are wired in such a way that they will only start working when the meter switches over to the lower tariff,this can vary a little as to the time it starts but it is usually around 12am-1am.
The heaters themselves will have 2 controls...input and output.Input is for how much you want them to store and output for how much heat you want to give out,they are variable.You will want to ensure that the output control is on minimum during the night so that valuable heat is not lost whilst they are storing the heat.Input to be set according to how cold it's going to be,set on max during the coldest months.
It will take a bit of trial and error at first I imagine to get it right but if the correct size heaters were installed they should keep you warm enough.
As you will be on the E7 tariff it may be worth investing in timers for appliances like your washing machine,dishwasher if you have it also, to run at night to take advantage of the cheaper rate.
