excuse if this is obvious but have you tried tightening the door pins?
Sooooo many are loose and rattle.
Other than that get your door card off but be very careful not to rip the bit thats bonded to the door card off.
Also be careful not to split the vinyl across the top of the door when pulling it out of the slot that runs the width of the windowl.
There is a rod that goes from the door handle to the door lock and that passes through a hole in the door and can rattle a lot.
Good luck, I just sorted a rattle on my dads Polo, it was the air intake pipe!