Gas is by far the cheapest for heating, since the cost per kWh is about half what electricity costs.
Most of the usage is for heat (electric lights and TVs use very little) so fan heaters, tumble driers, washing machines, immersion heaters etc with heating elements use most electrity, especially if they are run for many hours a week.
The reason gas bills are quite big, despite its cheapness, is that we use such a lot of it to heat our homes and baths. A typical modern gas boiler can have a max output of about 30kW, which is equivalent to ten electric fan heaters. Luckily they do not run flat out all the time. Modern boilers are much more efficient than old ones, but the installation cost means it takes some years for the savings to cover it.
A useful tip is to take your meter readings once a month or so and input them online (AFAIK all utility companies enable that now) so you will not get estimated bills, and you have the opportunity to notice if your usage is getting high.
Monthly paymnents can trick you, they are besed oin estimated usage, and if they have been set too low, then you will have a lot to pay at the end of the year. If they are too high, you are giving an interest-free loan to the utility company. So another advantage to you for inputting frequent accurate meter readings.