Geany is a nice GUI option. It’s a bit more capable but still lean.

It’s probably time for me to re-evaluate the host of coding editors out there. For the most part I just use good text editors. Though I do love Spyder, I only use it for a certain subset of tasks.

Yes, absolutely! I’m in a renter’s mindset so I didn’t even think of that.

In theory, the only difference between an electric heater and your computer, as far as actual heat goes, is the dispersal pattern. They will generate exactly the same heat: 1W of heat per 1W of electricity used. That’s thermodynamics for you!

You said:

The flat was kept not quite as warm as previous years

So I don’t think it makes sense to assign any of the savings to using your PC vs your usual electric heaters. It’s because you kept your place a little cooler, which makes an absolutely huge difference. When heating in winter, every additional degree of air temperature is more costly than the last, since heat loss is relative to the temperature differential between indoors and outdoors (i.e. a warmer room will lose more heat to the outdoors than a cooler room, so you need to generate more heat to maintain it).

This sounds to me a lot like dieting. Most of the time, the success of a diet has less to do with the actual diet and more to do with the fact that dieting has made you more mindful and changed your behavior in other ways.

The two biggest things you can do to save money on heating in winter are:

1. Keep your place cooler. Wear warm socks, long sleeves, etc. instead.
2. Improve insulation. Plastic window insulation kits are cheap and easy to install/remove. For doorways, you can get adhesive insulating foam to fill side gaps and a slide-on door sweep to cover any bottom gaps.