Take off the little clip that holds the two sides together, its located just under the rear of the seat pad. Then remove the small screws that hold the seat panels to the metal frame around the boot lid hole, you only need to remove 2 off these from one side panel, this will let you pull the front of the seat panels far enough apart to lift the unit off.
If you still have the plastic storage box attached its probably easier to remove the small rear panel and rear light before you lift the unit off.
A bit of lubrication on the grommets will help things slip back in as well