Personally... I'd ditch the idea of storage heaters... they require an E7 tariff to make any kind of economic sense out of them... and if you have an E7 tariff, then the whole 'way of life' needs to change too... with delayed start washing machines/dishwashers.
There's currently no indication that a super-cheap E7 rate will ever be offered again... and with the pushing of electric cars etc.... this will just make it less likely. If anything, it'll be scrapped completely with maybe a smart meter driven switch that'll dump cheap power onto you only when the wind blows too hard.
I know it's tenanted... but lumbering tenants with highly expensive heating is immoral in my opinion.
Sadly... I'm not aware of any sensibly priced electric heating system that provides the proper centralised controls that are needed.