There are many occasions when I have wanted to switch the interior lights off permanently, when cleaning out the interior of the car, for instance. The problem is that every time you open any door the interior lights all come on, and they stay on for 16 minutes unless the door is closed again or the dome-button is pressed. Fortunately, when reading up on closed-current problems I came across this:

Dome Button:

The lights of the interior lighting system can be switched on and off by means of the button at the front of the central light unit. However, the lighting is still controlled automatically by the general module.

This means the interior lighting, when switched off by means of this button, would be switched on again by opening a door.

As a special function, the interior lighting can be switched off permanently when the button is depressed for longer than 3 seconds. The system reverts to automatic mode when the button is pressed once again.

I've just been out to the car and given this a go, and sure enough it works! So when cleaning the car just press the dome button for 3-seconds or more and the interior lights will stay off when you open any door. The interior lights will only come on again when the dome button is pressed. It is possible that this only works on facelift models (just as the 'follow me home' headlights only work on facelift models) but give it a go.