hi, part of the outer walls are just 100mm (one brick thick). what i really want to do is add insulation to it on the inside , but im really tight for space. what i was going to do is build a stud partition using 50mm x 50mm timber ,fixing a 6mm sheet of ply to the back, leaving 20mm gap behind it.then filling in between with celotex and the use vapour plasterboard on the surface. i need to do stud work as it needs to support a false ceiling (not a large one 1.5m span). do anyone think thats the way to go .