My mum was looking into getting cavity wall insulation, but I read up on it, and it looked like it could lead to problems with dampness, so she's not going to bother. The government is pushing it with grants as a way to meet EU emissions standards, but a lot of people are reporting problems after getting it done, especially when they have houses built in the 20's and 30's like this house was, which were built without vertical damp-proof courses.