Recently I have noticed rainwater penetration in my Audi, occasionally through the overhead light, sometimes just appearing in the passenger footwell. The leaks started shortly after I had the front windscreen replaced at Autoglass. Could there be a link?
Have you got an aerial above the light on the roof ? If so - they sometimes become loose and water leaks through and finds its way down from there ? It could be the windscreen - take the car back and ask them to have a look or fix it as they always guarantee their work.