If what you say is true , what do you think the reasons would be for the quoted claims then ?
Uk gov. stats. claim
"17. The combined savings from insulation and heating efficiency improvements reduced
domestic space heating by an estimated 41.3 million tonnes of oil equivalent. Without
these improvements it is estimated that energy consumption would have been twice
as high as its current level." (table 6 shows estimated saving of insulation and energy eff.)
I think one may be many homes in the UK prior to the mid 70s had no central heating systems. Heating demand has increased due to the desire of occupants to have higher levels of comfort in thier homes ( perhaps unnecessarly high ).
Population and households i believe have risen over the time span you mention , though i'm unsure of the percentage increase.
edit : the summary offers some population/household increase info.
"1. In 2010, energy consumption from the domestic sector was 48,871 thousand tonnes
of oil equivalent. This was 31 per cent higher than in 1970, 19 per cent higher than in
1990 and 13 per cent higher than in 2009. The increase in 2010 follows a general
decline since 2004 and was largely driven by colder temperatures.
2. Some of this increase has been driven by a 17 per cent increase in the number of UK
household and a 9 per cent increase in the UK population since 1990, with a 1 per
cent increase in both household and UK population since 2009."
despite the estimated increase in demand ,interesting though to see these levels of savings were achieved even though theoreticial U value weren't achieved (due to poor implementation?) imagine what could be achieved with greater quality control.http://www.decc.gov.uk/en/content/cms/statistics/publications/ecuk/ecuk.aspx
this link may be more useful to study HB as it's a spreadsheet with a more detailed break down showing mean/medium for area/house type etc.
One thing that stood out was that houses built post 2000+ had a slightly higher mean gas use (main energy source used for space heating in the Uk ?) than those built in the previous period shown . ? Perhaps due to increase levels of occupancy per unit in new home ?