Here are my tips for reducing gas bills beyond the usual you see and hear on TV, radio and energy focussed web sites beyond just switch suppliers, insulating your cavity walls and turning down your hall controller by one degree. Being slightly cynical, you will save money the first time you switch and use a direct debit  monthly account, but after that most gas suppliers are pretty much aligned in their charges.

I had a habit of just extending the time the heating was on when it was very cold, which led to some very large usage numbers of greater than 150kW/hours a day before I changed my habits.

Heating hot water

Gas central heating