Range Powermax 155x-high gas usage!

I had recently received my gas bill and I was shocked how price has increased. I switched to npower last year and I paid every month DD £40 but now npower is asking me for DD £84 monthly (gas only!!!).

This is 2-bedroom flat with 4 people living in there. Normally we use a cooker more then heating - twice/3 times a day and heating for 1h a day, it's off during night time (this is really warm flat). There were maybe a few really cold days during this winter when we kept heating switched ON for longer.

Could anyone help me and provide some information how to set up Range Powermax 155x boiler to save more energy.
What is a best option for central heating and hot water?
I kept my hot water switched on continuously but central heating was regulated by thermostat.[/b]

Most economical way to run your boiler is with stat on '0'

Even with the central heating off, the Powermax 155 maintains the thermal store at about 80C with HW on constant.

You would save gas by running the HW in timed mode (three way switch on left of panel set to timed and programmer set up accordingly). This is the recommended setting as per the Manufacturer's instructions.

Thanks guys!