Same thing happened to me , I glued the plastic push rod back but the mechanism was then too stiff to naturally drop down on its own. The only way to fix this was add more weight to the rod.
A quick and easy solution was to use something heavy such as a few 1p coins you can add about 10-20 inside the device used to control the water flow level.
So the weight on the pushrod is really heavy. The only other solution was to repair the device but its going to cost you.
Simon
March 2011