Sorry I missed this one hope I not too late.
Simple answer first:- You use a transformer or power supply. They are nearly the same thing. The transformer does not protect from power variations and is heavy. The power supply uses technology called switch mode and will correct some voltage variations on the supply is lighter and has a minimum wattage as well as max so normally will work only one lamp although some versions are able to more. Very few transformers are still used but the old name is often given to the new power supply. The switch is always on the 230 volt side of the power supply.
The bathroom zones shown in links are outdated. There is no zone 3 except for saunas and zone 2 extends 2.25 meters above floor. I can see nothing in the regulations that includes the hand basin although common sense should restrict what is included there. There may be building regulations that cover this but the whole idea of new regulations is to â€œHarmoniseâ€