Double Dark Side! Diesel & 8P
It could just be a leaf or something that's managed to find it's way in.
I don't have a guide I'm afraid as I used the A3 Haynes Manual. It's fairly straight forward.
You need to open the glove box and you'll see 3 T25 torx bolts that fix the glovebox to the underside of the dash. Remove these, then remove the plastic panel at the end of the dash on the passenger side, in the same place as the fuse box on the drivers side. Under here you'll see more torx. You need to remove 2 of them (cant remember which ones) then the glove box will drop down.
Behind the glovebox you'll see the fan unit adn it is easily removed with a couple of philips screws.