Hi Jamie,
It’s interesting that your usage is highest on the day rate of your economy 7 meter, the appliance that eats the most electricity is (as discussed) this storage heater which should be registering against the night rate.
If the day usage on your bills is highest it may be that the two rates are being charged the incorrect way around. This needs to be checked as the rates being the wrong way around could cause the bills to be higher than they should be.
Again I can help you check this but access to your meter is required so this needs sorting with the landlord/caretaker as soon as possible.
I think that if you are running a storage heater at the rate times the night usage for your account should be higher than the day.
Have a think if we can check this, and let me know, I have sent you my contact details…
Brian