I have one wall with no cavity, so it could not be insulated that way by Hyndburn Homes.
I websearched for alternatives that I could use.
There are rolls of cladding that can be put on like wallpaper, but it would have cost me £200+ for one wall area about 12'x 8'.
I have used Thermilate - a paint additive - I do find it effective but not as good as the cavity wall insulation would have been
Insulating Paint Additive, Insulating Paint, Paint Insulation, Energy Saving Paint