Renault Espace lights won't turn off?

I have a 2001 Renault Espace. The headlights came on yesterday when I was not in the car. They could not be turned off. The key was not in the ignition. I tried turning the lights on/off switch, tried starting the car - nothing worked.
In the end I removed the fuse, which did work, though also turned off the radio, which should have been a different fuse.
Help!