British Gas is currently installing free loft and cavity wall insulation (subject to some checks) for anybody regardless of income. There are no tie-ins with British Gas and they will also replace hot water cylinder jackets.
There is a charge if they have to erect scaffolding to complete the cavity wall insulation.
The energy advisor Mark used was Ed Stebbing-Allen and he would be happy to speak to anybody who is interested on 07769 549 234. Below is the relevant information copied from the British Gas website.