man you must be desperate for better speakers!
i googled it and found this thread: http://www.focusstoc.com/forums/topic/119224-removing-rear-interior-panels/
if you cant see it let me know and i will paste the details on here.
sod it i'll do it no
There are 2 fixings behind the 'B' pillar seat belt adjuster another behind the rear seat back pivot and one more at the rear, then it just pulls off.
Trouble is, the rest of the trim around the window needs to come off first or it becomes rather difficult.
the seat belt adjuster has a small cover at the top that reveals 2 screws, mind you don't drop them.
Also you won't see the screws if the belt adjuster is at it's highest position as this will cover the screws
The trim at the top has three screws under the long cover that hides the curtain airbag.
The trim at the rear that the parcel shelf sits on has 2 torx screws underneath.
no wonder he spends all his money on the car lol