Guess what, after a night shift my first low power staircase light time switch device is working as desired. 
The power requirement is a bit strange, I've expected a low value but not that LOW.
Being connected to the main line with 230V/50Hz the meters say that the whole circuit consume only 22mW (should I trust my meter?).
The micro from Microchip is running with 4MHz and never going to sleep, the datasheet say 360µA at 3V this is 1mW for the micro.
Then the power supply and some leakage of the peripherals consume 21mW, I'm not confident that I can reduce this more.
... but anyway this doesn't sound bad, or?
So what should I build next?
Regards from the Vogtland,
Andreas
PS: If you have any comments or hints. Give me a comment