Bamhan,
Im faced with the exact same problem from classic. At least 3 car loads (but will try for 2) of cardboard and polystyrene to get rid of after delivery of furniture. I rang the shop and they said they do not under any circumstances take back packaging.
My plan to get rid of it is to cut up the cardboard into manageable pieces, go to ballymount civic amenity centre and recycle it for free. They will charge for for the polystyerene as its not counted as plastic, I got hit with that on a previous visit. 12e per car.