1 We have a plastic kettle because it's light. I bought a similar kettle for my Nan years back and was amazed at the difference in kettle weights available. She could then make tea much more easily. More weight means more material needs heating as well as the water.
2 I bought a new thermos earlier this year, a Thermos Ultimate series. It's the best flask I've ever had. If I leave it in the shed overnight I can still make tea on day two, I'm fussy with tea too. But more to the point, it's supposed to be more energy efficient to fill the kettle totally up then use it from a flask whenever you want a brew. I started doing this a wee bit, and also discovered that you are obviously no longer waiting for the kettle to boil, you just pour the flask and there's your tea. Weirdly satisfying to not be waiting.
3 Also, kind of almost related, I had always thought it was a thing that an upright fridge or freezer was wasteful because the air you had paid to chill falls out every time you open the door. I read someones experiment to see if that was the case and it was so tiny as to not be bothering with. They calculated, for comparison, after a warm or hot bath do you pull the plug? You would save many times more money than the fridge loses by leaving the water in the bath when you have finished until it had given up it's excess heat to the house then drain it, or you are paying to heat your drains! You do get more condensation though.