Hi Mark, it was built in around 1963 and is probably about 30mm wide with a gale force 9 whistling through!
I do thermal imaging and I have seen cold air penetrating behind dry lining in a number of new builds. In this day and age with building regulations supposedly tightening up why are these things not being addressed. I think a full survey of a new property should be carried out by someone who knows what they are looking for, including air tightness and thermal imaging, before a building can be signed off and it should be either a pass or a fail instead of "that will do". If it is a fail the builder should be forced to strip out the building, rectify all the identified issues and pay for a second survey to be carried out. They would only have to do this once because the first fail would be so costly that they would never want another!