There were ~11 million homes in England in 1939, and ~23 million in 2019. Even if we allow for single homes being split into multiple smaller ones, and assume t

There were ~11 million homes in England in 1939, and ~23 million in 2019. Even if we allow for single homes being split into multiple smaller ones, and assume that every 1939 home was still standing in 2019 (ignoring the effects of the Blitz, and of the slum clearances of the 1950s and 1960s), that would still suggest that half of English homes are less than 80 years old. I doubt things are significantly different in the rest of the UK.