Hi any advice on the best way to insulate the walls? Built from single skin of hollow 9" concrete blocks it's a common type of semi around west norfolk. I think you can inject the hollows with foam (saw a usa guy doing it on youtube) but worried that it will not work well as it won't be a complete insulation layer. On the other hand I read that external insulation can get air circulation in the block hollows carrying heat out into the loft, even before it hits the new insulation. Has anybody any advice on the best way to insulat? I don't want internal as it's too inconvenient. Cheers - Rich