After looking at the photo, and before actually reading the post, I was sure it was a switch for retrofitted fog lights - they are not required in the US and you must to have them in Europe in order to pass MOT.
I have an almost identical looking switch in my Mustang (which I imported from America) and it does exactly that - turns the fog lights on and off :)
I have an almost identical looking switch in my Mustang (which I imported from America) and it does exactly that - turns the fog lights on and off :)