If you remove the door card there is a strip that runs along the top of the door that pushes against the glass.
If this strip slides forwards towards the wing mirror it leaves a small gap at the back where it joins the vertical seal. This whistles like a biatch, but as with most things if you work for Seat you can't hear it!
I just slid it rearwards so that it joins the vertical seal properly and the wind noise disappeared.
Hope that may be of some use!