Removing the seat headrest on a 355

You see the two black plastic circular things that your head rests go through into the seats? Pry them both out from the seats so there freely sliding up and down the crome bars of the head rest. Then tug hard on the rest and it will pull out. They do need a sharp tug mind, and the plastic sleeves have to be pryed out or they will not come out.

 

There are 2 metal chrome clips that prevent the headrest from fully coming out. If you gently pull the top of the horizontal cushion (this is the inner part of the seat you rest against) toward you, you can gain enough access to remove those clips with some needle nose pliers.
The head rests will then pull out with no drama.
You do not need to remove the plastic grommets and when you reinstall the head rests you can leave the locking clips out if you wish.