We estimate that by the end of 2008, approximately 10 million homes in Great Britain had received cavity wall insulation, leaving around 3.5 million homes with cavities still possible to be filled without significant practical difficulties. Approximately 600,000 cavities were treated during 2009, taking the total number of filled cavities to just over 10.5 million and leaving an estimated 2.9 million homes with cavities considered practical to fill. The Government have committed to filling all cavity walls, where practical, by the end of 2015.
Further information can be found in the 2008 English Housing Survey, and in the Government's recent Warm Homes, Greener Homes strategy and supporting documents.