GolfTi - I'll try and explain it better lol
Excuse me if I'm teaching you to suck eggs. The way the headlight washers work is that when the lights are on, the first time you pull the stalk back it will wash the lights and windscreen and then every 5th wash (I think you need to be on a pretty long journey / dirty road to be washing your windscreen 5 times, in which case a bit of soap on the bonnet is irrelevant). So when you are just doing normal driving at night this works well.
If you just pull the stalk back for a split second (i.e not enough time for any spray to actually come out) you will see the windscreen wipers start to wipe as they think you have just squirted washer fluid. That is classed as its first whipe so when you do it again it WONT do the headlight washers and will just do the windscreen saving your bonnet and giving you a clean windscreen

Capice?