On we say pane, as in single pane and double pane. Ah, Wales, such a lovely country at least looking at pictures of it. I wouldn't want to endure rainy cold all year. 

Our house is like that though, with single pane windows, no insulation between the old wooden boards and drywall and lots of cracks and gaps due to shifting foundation. The ground here is black clay that expands and contracts a lot and it plays hell on any type of foundation. It's been a pretty cold winter for us in the southern States. Though most of the year it's hot and holy shit it's fucking hot.