Economy 7 Storage Heater Timing?

Pennywise

Anyone know what to do about storage heaters that aren't coming on every night. They work probably 4 nights out of 7. There is a sealed box next to the meters etc that has a label on saying that the power is turned on by radio control each evening, but there is no contact details. I've tried calling our electricity supplier, but they deny all knowledge and say it's down to the "grid". I've phoned a few other numbers but no-one can tell me who's responsible for it. I need to know whether the box itself is faulty or whether it is their "radio control" centre that is not sending out the signal. Anyone got any ideas where to go?