Yes, there are alternatives - for example, I personally use LPG, because I don't have piped gas.We will have to agree to disagree on that point - There are alternatives to mains gas or off-peak for heating, such as stored gas, oil and traditional fuels like coal and wood.
However, we perhaps do have to disagree about your apparent implication that by manipulation of day/night electricity costs, suppliers could induce significant numbers of people to change to heating by off-peak electricity if they were not, for whatever reason, doing that already.
Kind Regards, John