My balanced flue Cannon Coalridge gas fire (model 26621G) lights OK and continues to burn as normal for a minute or two (occassionally up to 10 minutes) and then cuts out.

I would be grateful if someone would give guidance on what may be wrong.

Additionaly, if you able, I would also be grateful for advice on how much it is likely to cost to have it repaied.

Thanks for your help.

Sean Ronan, November 2011