I'm at a friend's house in Seaford (in England, near Brighton), and thinking of you because he has a light switch outside the bathroom (I don't know why the English think that if you have a light switch *in* the bathroom you will perforce electrocute yourself). He said, "Just hold your finger on it until the lights do what you want."
The switch is a little metal sort of button. It's not entirely comfortable to hold your finger on it.
It also turns out that "until the lights do what you want" is incredibly difficult to time correctly -- and it has to be precisely correct. It's fairly easy to get the lights to turn on part way. It's not that hard to get them to turn on all the way. It's incredibly hard to get them to turn all the way off without coming back up again.
The switch is obviously meant as a test for drunks. If you can't set the light properly you are in no condition to use the bathroom -- you should go outside and use the bushes.