Your boiler is failing to light the gas burner or is losing the flame while it is running, meaning you will have no heating or hot water.

DIY fix possible

Check if your gas supply is active by testing another gas appliance like a hob.If the weather is freezing, check if the white plastic condensate pipe leading outside is frozen and thaw with warm water.Press and hold the 'Reset' button for five seconds to see if the boiler restarts.