You need a new switch (whole stalk unit), same thing happened to me and its really anoying and dangerious its a common flaw in 206s, wd-40 fixed it for a while but only a few weeks. You might be better of with a new one a scrap one could be the same. Not a big job to fix very simple, but a dealer could rip u off for the part. note some citroen parts might do...
Sparkz
May 2009