(FWIW, Sweden's neighbours like Norway, Finland and Denmark also have houses where it's warm inside in the winter without horrific leaks. And yes, Iceland, even if it has practically free, abundant geothermic heating energy.)
(But what horrifies me in England is not the wind through walls and puny glazing, it's the carpets in bathrooms, including around toilet seat. Experiences are not recent, though, so perhaps they've changed?)
I was referring to retrofit, sorry for not being clear.
Also, the costs are not passed on to customers. Very few houses in the history of the world have been priced according to what it cost to build. The market sets the price.
Carpets in bathrooms is a kind of baby boomer 1970/80s thing I think - plenty of it still about. Check the corners of the room where condensation pours down the wall into the carpet... after a few years you get a nice dark grey brown mould line.
But still, it's not the government that carries this cost.
Retrofit cost goes to government if the government decides to subsidize it. I live in Finland, which is considerably colder than Britain, not to mention Australia, and here the requirement for insulation is simply mandatory in building permits (which is required also for major renovation, not just new houses).
There are no real subsidies for this. Also, there are no heating grants which I hear are a thing in the UK (and a thing big enough to have an impact on how people vote).