If you fly Y there wont be any closet for you available on A380, only with good will of the crew. And I wouldnt count on it. Why should they stow something in an F closet that is assigned to a seat/pax for somebody travelling in Y?

Since the introduction of the new euro cabine (NEK) there are no closets anymore on the short and midhaul planes.

Your best option: get a sturdy garment bag or suitcase and check it.