The answer is that I don't actually know except for the following:

My friend in the UK had the previous model XJ and the cover of the back seat had come off.
I'm pretty sure that it was held on by some type of clip which had broken but the back panel was similar to the x350.

I'm guessing that there are four plastic clips around the panel and it's a matter of inserting a thin flat tool behind the panel,locating each clip carefully and levering outwards.

I suggest also that you could do the following:
Ring up the stealer and ask for the workshop foreman then ask him how to remove it, without breaking the clips.
This has worked for me in the past

 

Thanks roberwil for the reply, looking through earlier posts I found: "I was trying to remember that ! By the looks of the rear trim, you pull it away from the seat at the top, pulling xmas tree clips out." they also placed a photo: http://img.photobucket.com/albums/v321/ ... CT7049.jpg

But having a look at it, and not wanting to damage my pristine interior I'm going 2 get my local expert 2 look at it