As I understand it, if you have a boiler in the kitchen or somewhere similar, with a timer attached to it, and a pilot light visible through a little window at the front, you may well have gas central heating. If the boiler does not appear to have a pilot light, you might well have electric heating.
(For the purposes of completeness, if there is a big tank outside in your garden, you probably have oil central heating).
If you have two meters, one for electricity and the other for gas (which measures in therms), this is another clue that something in your house expects to use gas, although it may be the cooker, of course.
The economy 7 might just relate to one single storage heater somewhere. These tend to be quite big and bulky, as they have bricks inside to retain heat that is gathered during the night when the electricity is cheaper. They do not look like radiators.
Are the radiators you talk about wired into the wall, with switches, or do they have pipes running back to the hot water tank/boiler set up? This is another possible clue.