Hello,
I've read a previous answer about my problem, but I dont know what size I need to enlarge the hole to, It's about 5 x 8 inches at the moment, do you know the regulation size it should be, I have a back boiler and baxi gas fire in front of it, the room is 11 x 18 feet, by the way this is not a Corgi thing where I need certificate is it, as I thought I could do this myself, the heat output of the gas fire is 3.8 Kw and the boiler is 16 Kw.
Many Thanks.