I will go with your first approach. Can you please look at the script that I got from Internet (see above)
I need to latch the relay when I get the signal from PIR ( yes after removing the LDR and installing it externally)
Is it possible to help in modifying the script to work with your suggested PNP solution.
The way I am visualizing your approach is; The signal from PIR will go to the base of the PNP with say 1 K ohm.
The collector will control the Relay, And the relay will LATCH the lamp ON.
If I want to switch the lamp OFF I will use the physical switch .
Of course life in NOT that easy; because of this dumm switch status. ( is it ON...Is it OFF ???? )