If when you shut the door you hear some rattling, you will find that the window lifter has rusted through and the window is not sitting in the "F" runner bar, it will cost around £30 for the "F" bar and the window rubber.
To replace you will have to take the whole window assembly out of the door, it will take 2 of you to put the window in the lifter bar and rubber as it is a tight fit.
It took me about 2 hrs to do take the assembly out and put it all back to gether, getting the motor lifter arms back in to the lifter bar was a real pain in the butt.
But have fun doing the job, it is reqarding to see the window go up and down again by the switch and not by hand!