Warning message re lights?

I have an 07 citroen c3. I am constantly getting the on-board computer bleeping and telling me lights aren't working. It goes on a cycle through them all (brake lights, indicators, reversing lights, fog lights, front lights) followed each time by "info faulty". This has being going on for about 6 weeks. About 3 weeks ago it was in the citroen garage for a safety re-call to do with the lights (apparntly some were switching off while you were driving). I am really narked with the garage because they refused to look into the fault I was having with the lights at the time it was in for a re-call. Does anyone know why I am getting all these faulty messages (and yes we have checked all the lights are working, which they are)