.....OK....
In all seriousness - most sunroof motors have a manual drive function.
Now is this a very late P38 (51 plate upto March 2002) or a very early L322 (02 plate onwards)????
Both have a manual drive function as far as I am aware, just pop out the roof light plastic surround by the rear mirror and you should find the sunroof motor....wind it until it closes fully, this may cure the leak....
Whilst it is now fully closed and not leaking, time to check the switch and power thereto (Fuse, etc)....
Download the RAVE Manuals (search on here and ye shall find) and this will give you the electrical diagrams to follow....