Light switch front plate - wiring complications

[KittieCadaver]

Our wiring is pre 2004, so we’ve got red, black and green/yellow wires.

I’ve replaced a 1 gang light switch front plate today as the rocker switch was failing. I’ve put the red in Com, black in L1 and green/yellow is earthed in the back box, which I’ve not touched. All good.

This is how it was (bar the fact the com is now at the bottom in our new MK faceplate instead of at the top as per our old one).

Being a belt and braces type I thought I’d just double check how the bedroom switch is wired. I’ve not touched that one - but the black goes into the com hole in there. See pic

Does it matter? Am I going to burn the place down or is the old one wrong?

These jobs are never as simple as they should be...

Doesn't matter as technically they are both "red" but often the black "red" is not oversleeved as it should technically be.
You can get double brown cable (used to be double red) for that reason.

Thanks very much, @johnd2. Electrics make me nervous, despite this being a very simple job and me not being entirely daft! Much appreciated.

The two cables are live and switched live that allows you to turn the light on and off. The switched live should be oversheathed or a bit of electrical tape wrapped around it to show it is a switched live.

There are lots of really good videos on YouTube for UK electrics where you can double check. Pouse around the House, How2D2, Ultimate Handyman and the best is GSH Electrical.

I love your belt and braces attitude which is exactly what we do too.

Thanks for those recommendations, @JacksPottedPepper really helpful and much appreciated.