In my 2 F A380 legs in April as a Plat I was given preference for showers both times (and in fact, in one, I did not get my desired slot as another Plat and his "Gold partner" had been asked beforehand, so I was 3 on the list of 14). Food is dine on demand, so does not really make a difference, at least in my experience.
With regard to food being dine on demand not affecting availability of your preferred choice I submit that in my experience it does not stop your choice or choices (or in my case on ultra long hauls any food or soup at all - must have been some very hungry people in F that day as their were only the ghastly rolls left) still being available when you want to eat. I have routinely asked them to set aside my preferred choices as soon as possible for a long time now. Have not been proactively asked though as a Plat.