Roof leak in 206 convertible?

I've got a 2004 Peugeot 206cc.
Since few days, everytime it rains (pretty much every other day here, in UK) somehow, somewhere water gets and when I turn the car at high speed - drips through the roof light. Every time it happens - I'm unable to use the central lock on My key (I'mforced to actually use the key to lock it, so alarm isn't active), as alarm goes off, so I'm guessing the leak messes up with the wiring.
I've opened the roof, but the seal seems to be dry.
Any idea, what can be the issue ?
I thought maybe an antenna or a seal on the windscreen.
I'm really new to the whole hard-driving thing and I wouldn't want to strip the whole interior apart.
Any help or advise would be greatly appreciated.