check with your council
我们这儿的council有grant for cavity wall and loft insulation。 有专门的公司来做,统一价, detached 贵一些,semi的便宜些。house比 bungalow 贵。council有补贴,为了鼓励节能。 我记得cavity wall 是269。free for pensioner and low incomer. my neighbour a elder lady had all done for free.