"Martin Bonner" wrote in message
...


Cavity wall insulation didn't become required until the 70's,

It wasn't required in the early eighties.
Until about three years ago I had the only house with cavity wall insulation
in the street and I had to pay for that in 1981 just after the house was
built. Quite a few have been done now its subsidised. I can't moan though, I
have saved many times the cost in thirty years.

which is
hardly "very old". In fact, it wouldn't surprise me if the majority
of our housing stock predates cavity wall insulation.