agree completely, but it's easier and cheaper to build new than retrofit. It'll take decades and decades to get older houses greener, but we can improve the quality of the overall housing stock by ensuring better build quality, solar and air/ground heat pumps in new houses
Retrofitting loft insulation is extremely easy, an amateur could do that and get good results, and that stuff they pump into cavities looks simple enough too (for a pro).
Not sure what you do about old houses that are just a brick wall, and nothing else mind. Suppose you could timber them out, insulate and board them, for the external walls, but it's a lot of cost/ hassle. Also everyone whose gone for that "back to brick" look, won't be helping too.
I don't think heat pumps are well suited to our climate from what I've read, but that was a while ago and I may be wrong.
For me I'd be looking at giving people loans, to carry out green projects on their homes for changes which would make a big difference. Then the loans get paid back, by what they would be saving on energy bills. Effectively if a project cost 3k, and saved £300 a year, then the government pay the 3k as a loan against the house, then if the consumption changed from 100kW to 70kW then the energy company get paid for 70kW, and whatever 30kW is gets paid back off the loan. If that takes 10 years, and the people want to move after 5, then the remaining loan stays with the house, and the new guy takes over until it's paid off. I really can't think of a reason why this would not work, and how it couldn't lead to less energy use and cheaper overall bills for everyone in 5-10 years time.
A lot of the reason people don't do green things, is because they can't afford the initial outlay, or may not see themselves in the house in 3-10 years, so they don't want to foot the bill for someone else's gain. If everyone did it as a collective, then everyone wins, and we do far better on our co2 targets.
I can't think of any reason why new houses shouldn't all have solar.
Could also have a scheme where all new developments have to carry out a green project, of similar scale. It wouldn't necessarily have to be on the same site, we could allocate land for major wind turbine schemes, and new developers 100 miles away can chip into the pot to fund it. Could also get new developments to build a solar roof over areas of SUDS ponds, attenuation tanks and pumped sewer (rising main) stations, etc. Nearly every housing project has these, and effectively unusable land directly above them which could be put to good use for solar panels, which could run the local street lighting.
Street lighting should be on proximity sensors by now also, if someone is walking, light up a few posts ahead and a few behind. Same with motorway lighting, it's not necessary in the middle of the night when there's low traffic.