Disco 3 (LR3) Dripping water from door /windscreen pillar

This is the latest niggle. On wet days i have a brief dripping issue on the drivers side door/windscreen pillar . It only last for a couple of minutes and goes . Normally it seeps from headlining from behind the sun visor or more recently from the airbak plastic cover 3/4 up the door/windscreen pillar . I have not yet investigated but my gut instinct is that a water way / gully is blocked in the top corner of my roof above my driving position . Any thoughts anyone?

Have you a sunroof?

Yes a full panaramic sunroof with roof rails