Had the same problem with my n/s front window, I seem to remember fitting the entire mech before finding it didnt work .
Fortunately I was still at the scrappy so I oiked out the drivers side switch assembly and hey presto it worked! Seems a trip back to the scrappy may be nessesary.
99 HDi Estate 110 fast approaching 200K. edit: now 215K
the drivers side switch can occasionally let the whole side of the electric windows down, what i found to be the problem is that there are clips holding the whole switch bank together, they can break and when the switches are used it moves the unit apart meaning the buttons dont work, so a bit of selotape can usually fix it well, although superglue fixes the problem better