The Uk hasn't really built houses for any season very determinedly, at least not since the late 1800s. Since then, we've been fluffing about with various things, none of which are really good enough - they weren't good enough when spec'ed, and aren't good enough now either.
The UK is fast becoming a more summer country than winter, so your advice isn't crazy. However, people think insulation is good for the cold, and we need lots and lots of it - in very little tiny gap an orifice of every building we have.
As a bit of an example, we internally insulated a bit of our house, and since then, those rooms are warmer in winter and cooler in summer. Our neighbour went the whole hog and put 100mm of external insulation over most of his house and since then, he barely needs the heating in winter and if he keeps the blinds closed, is doing pretty good in summer too.
External blinds are probably going to be the Next Big Thing in the UK though. Right now it's actually hard to find anyone who will fit them - there are people of course, but not many. One day we'll do some external insulation on our place, and we'll 'bury' blinds in it.
As for heat pumps with cooling... that's a much harder problem. Getting some pipes around your house is one thing, but getting piped air is a whole other level of problematic. It's probably easier to fit ordinary air conditioning in a lot of cases than it is putting in "central air". FWIW, I looked at getting some infrared ceiling heating and cooling into our house - it's a royal pain to retro fit, and then has lots of complication to look after forever more. It seems there are no easy options for retrofit.
Whatever the case, you know it'll be decades before the government mandates any of this sort of thing on new builds. You barely get an EV charger - or even the ability to ever have an EV charger at any time in the future at the moment. Getting insulation and air con (of whatever type) seems like a long way off. The only way you're going to get all this sort of thing in place is if you self-build, or otherwise tear your house to pieces to put it all in.