Further to this guide - http://briskoda.net/technical-guides/how-fix-noisy-fabia-ventilation-fan/65038/

I decided to stop them getting in there in the first place. Fairly easy to do.

First off remove the panel under the wiper arms. This involves removing the wiper arms. You will either need a small puller or the strength of he-man. Having previously removed and greased mine they came off with only a jiggle. The panel is secured to the base of the windscreen with one big long clip. Pull the panel and 90 degrees to the windscreen to remove. The three trim clips will snap when you remove them. I replaced mine with Halfords own. Once you've got that off there is another smaller cover over the blower motor. 2 torx and you're in.

Now you can see how the leaves get in. It's just a great big hole.

Using a piece of mesh cut to size I taped up the sharp edges. Also gives the other tape something to stick to.

Then I taped this into place over the hole. The tape used is waterproof duct tape.

Sorted.

Very neat job, well done.

nice one.