We've been slowly upgrading parts of the house for years, towards being more sustainable, partly in light of climate change.
When we first moved in, we got the best double glazing on the market at the time to replace the rotting pine single glazed windows at the back. When the windows at the front were replaced, we got the thicker double glazing available at that stage. (I do want to re-do the double glazing at the back, to either far better double, or even better - triple glazing, at some stage in the relatively near future).
When we converted the attic and built a rear extension, we put a lot of additional insulation into both (almost double what was required at that stage), which made a huge difference to energy efficiency. We also put insulation into the little roof over the north facing rooflet over the sitting room window a few years ago (original house has almost no cavity wall insulation - per original building regs when it was built, and that extended front window/rooflet had no insulation either).
The extension to the rear is built to have a lot of sunlight coming into the house, which is great for light and winter heat. We are thinking about putting up a "brise soleil" though, to take out some of that heat as summers get brighter and hotter.
We have a small rain butt in the back garden, collecting from the extension roof. I would like though to get a much larger one to collect from the main roof as well. We mostly use the collected water in the garden for plants and things like washing patio/clearing drains etc, but have used it for toilets etc when needed when we've had water outtages. Back when the "beast from the East" caused so many leaks that we had no water for about a week, and then many days of intermittant water/reduced pressure etc - it was a real saviour! I have also used it on occasion to try a small amount of relieving the system when we know very heavy rain is due, as we'll empty it beforehand (when drains are not overloaded) to take as much as possible when the downpour is at its worst. (I know, makes a minute difference, but every little helps).
We have a lot of plants growing both front and back. Including a few mature trees (we planted 2 of those almost 20 years ago, 1 was already there). And a beechwood hedge between ourselves and next door between the concrete drives.
We had already replaced the gas boiler for the central heating to a very high efficiency one. And having previously used a chimney balloon when not using the open fire to reduce draughts, we replaced the open fire with a wood burning stove about 4 years ago. So either it's fully closed and blocking the draughts, or burning a much more efficient fire for heating the room (and house - we open the doors as that room gets too warm now).
We have recently put in PV solar panels on the roof, so are generating our own electricity. It covers our base load during the day (the fridge, running 2 computers, having a light on etc), even on a cloudy day. On a sunny day, we can also run the dishwasher or washing machine (we set them on timers to follow each other), and still have energy going to heat the hot water tank - we usually are sending electricity back to the grid in the afternoon on a sunny day as the tank is at max and we are covering all we need. We have space to fit 1 extra panel up there, so will do that soon - intending to get an electric car in a couple of years, but also charge up bicycle batteries once we start back to work shortly (we'll charge them in daytime on WFH days) etc. And any extra to the grid meaning less need for gas-powered electricity for others is good.
We've always been conscious of choosing high-energy rated appliances, so everything is A+++ and we have changed almost all the lighting to either LED or solar powered (or both) around the house.
We changed the old air vents, which couldn't be closed (some intentionally, some just so badly fitted) so basically were always letting cold air in, to ones that had a far better seal around the hole and also could be opened and closed much easier. So not only will it keep warm air inside in winter, we can open them wide to allow air movement in summer.