I seem to remember there being two cables in one of the terminals on the original as both had the connectors up. Other than that, it was trying which combination worked in the correct way without affecting the rest of the circuit.
I took off the switch in a bedroom to replace it with a dimmer switch. When I removed the switch (after turning off the supply) I noticed that there were 3 lives wires.
The earth was connected to the back of the metal box. There were 3 neutrals, that were all connected together and fastened in...