My century-old house has double glazing, knee-deep loft insulation ... and solid walls. The only option I know of for these is dry lining, such as I installed long ago in my bathroom to great effect. But fitting it throughout the house would involve much more than an interior makeover - and too much bookshelf and cupboard space would vanish. So I'll wait until I'm gone and let the next occupier deal with it.

By the way, what's BER? In my universe it's usually "beyond economic repair".