Hi,    First post, but hopefully i'll be back for more having discovered this forum.   I've got a 1969 built Detached house, ground floor is standard of it's age cavity which has been filled at some point (looked to be in ok shape when I had some doors replaced, and first floor is tile hung single skin. About 2 years ago I started the process of IWI of the first floor with battens and 50mm celotex, which has massively improved the comfort of the floor, but now the ground floo