UK Pre 2004 UK light switch swap

[midderstristan]

They are push-wire terminals which only accept one wire each, so the common is doubled to allow a loop-through. Put both red wires into the one common terminal in the new switch.

The most logical expalanation of what we see is that the switch cable from the light(s) is the 3C+E, carrying PL, SL and N. The T+E is either the feed, or it is taking PL and N on to another point.

Thanks, that is really clear