Hi,that looks like a pre-payment type meter,with timed,relay outputs,for that contactor below. I'm guessing you have not been hearing it "click" at the start and end,of your E7 period?
There should be another main switch and fuse box,between that timed output,and the storage heaters.
Your electrician should have isolated and tested,at this fuse box,regardless of the time of his visit.
I am not certain of Eon's set-up,with regards to charging....and your contract or bill,may shed little light...(been there...) but the meter would seem to switch the E7 heating on,during your allocated period,this would then still be metered,through the meter,but whether this is at the normal or a preferential rate...who would know?
Sadly,attempting to furnish oneself,with the relevant information,from Eon,can prove..."testing",and i have in the past,had to hand out details and training,regarding almost every single part of their disjointed,shoddy service....to the point where i was drawing circuit diagrams,on box lids,for out-of-depth meter fitters....anywho
I would get someone clued up,to test your heater circuit and units,and triple check the meter arrangements,regarding actual payments,times and contract agreements.
The fact that you believe there is no functioning heating,yet the bill is increased,would be a good starting point.