My rear window on my '99 1.8 XEI needs to be helped home when closing tailgate. basically, I think its been replaced at some point and now it catches the edge of the top groove and stops there.

I am being lazy as I haven't even bothered to take trim off and have a look, just thought of it now as I was browsing this forum. Anyone had the same problem?

Remove rear trim and membrane underneath.
At the bottom of the door you will see two silver 13mm nuts on slotted setscrews at the bottom of the window runners.
Slacken off nuts and adjust the set screws ( anti clockwise in your case ) to pull the window top in or push the top out . Tighten lock nuts and replace membrane and trim.

Ta