Best answer by woz
Im a bit confused by your post, if you have the heating on a timer then are you sure you are classed as economy 7 and not economy 10?
There are 2 possibilities as far as I can see, either your heating is controlled by a time clock, in which case all you need do is override the clock, or it’s controlled by the meter switch itself, in which case it will need to be rewired. If I were you i’d find a friendly local electrician who will have a look and advise. With economy seven you are at liberty to use appliances when you like, but if it was wired for a tariff other than economy 7 the system will/may have seals on it which is why i’m asking as to why you believe your heating isn’t configurable to be as you wish.
sorry if post is a bit disjointed, post back if you need more info