Rear passenger near side leak (vectra B)(1995)?

Rear passenger near side leak (vectra B)(1995)?
Very recently every time it rains my rear passenger near side gets quite a significant amount of water in, have no idea where its coming in but assuming its coming from the door, checked windows and closed propperly etc but all ok, and ideas or how to fix? im all out of them now, many thanks

Nathan

nath
February 2010