We have had cavity wall insulation put in by a company which had a link through the council page - it cost £49, and there is also the option to get the loft insulated for another £49. This applies to both council and private housing, since we are council and my daughter has had it done and owns her house. The man came and did a test drill to check whether the walls were suitable, then made the appointment, and two workmen arrived, on time, and did an excellent job. Took about 2 hours. Well worth it.