Here's my contribution of personal installation experience. This diagram is for both TIMER UNIT & LIGHT SWITCH to work on "either one" mode. The TIMER UNIT will start to work once the 1 GANG switch is turned OFF, also user can turn ON the light at any time of point using the 1 GANG switch.



Hope it helps everyone

Yes of course, that would work too u can move the L1 flowing from 4 to 2 also, connecting LIVE to LIVE will not harm the electric flow circuit

I've made such diagram to not to congest port 2 since incoming supply looping to 4 has 2 wires attached, and L1 will make the port looks bulky, therefore I swapped with 4, this will look more neat

Easy, in this case you need to pull an auxillary 1 gang switching power supply which also connects to the device. This will ease to you use the light at daytime by turning ON the switch.

You can pull NEUTRAL line from any nearest available point