Thi applies to all Xantia Estate owners .. check under you boot mat and see if its damp.. also have a check under your rear seats to check for damp there. If you find some water under there then here's a permanent solution.
I was fed up with taking off the plastic inner on the boot door and having to reseal it every winter.
The force with which the door get closed seems to tear the seal away from the door especially in the central area where the plastic seal has to follow the indent for the lock
The solution was to use a strip of hard plastic,( I used the flat bit of cable ducting) cut it into appropriate lengths and drill small holes through it at appropriate intervals. Then screw some self tapping screws through the plastic and throught the sealer into the door.
It doesn't look very pretty in the photo above .. but no one sees it and it works.
There's always the option to reseal with fresh seal before you do the drilling .. I used butyl sealing strip, which seems pretty close to the original and compresses well under the pressure from the plastic and screws.
