In our last house, a 1930's semi, we took up a offer from British Gas to have our house insulated free of charge. They did a survey, which was fine, and a date was fixed for the work. When the firm that British Gas used to carry out the work actually came to do it, they refused on the grounds that BG had not told them we had an extension with a flat roof on two sides of the house. "we're not allowed to go on flat roofs". We told them it was reinforced, and that the BG surveyor had been on it, as had various workmen and builders from time to time, but they were adamant. I was furious and took BG to task in no uncertain terms. They said they would find another firm, but despite my chasing them up, they never actually came back with an alternative. Shortly after that, we sold the house. The extension was actually better insulated than the house! I think it would have made a considerable difference to a house which was always cold in the winter.