Have you had the fire checked out by a Corgi registered gas fitter? Modern gas fires are fitted with a safety device that will shut the fire down when, for example, the flue is not pulling correctly which can result in high carbon monoxide levels in the room.
The following extract is from the 339 Owner Guide:
"The Oxysafe flame sensing and flue blockage safety system.
For your safety, this appliance is fitted with a flue blockage safety device that will shut
down the appliance in the event of abnormal flue conditions. This device is NOT a substitute for an independently mounted Carbon Monoxide detector.
The device will also automatically shut off the gas supply to the fire if the pilot flame goes out due to lack of oxygen or for any other reason.
If this device starts to repeatedly shut off the gas, get expert advice."
Pip
December 2007