Really odd one this IMO. My friend has got a little corsa, and when she switches the sidelights on, its fine, but main beam and theres this really strange clicking that comes from the drivers side of the engine bay, but if she puts her full beam on, it stops??
I looked at it earlier and after saying I didn't have a clue what it was, it slowed down and stopped, but apparently it started again after she drove out of my road lol.
It's really quite loud, the engine doesn't need to be running for it to do it either.