On the lower rear trim piece in the boot of my X350 (04 XJ8), I found two small compartments. I opened the one on the right and it just looked like a small compartment to hide something small in. I opened the one on the left and SCORE! The cover has a multiple assortment of replacement fuses and a fuse puller. This is probably noted somewhere, but is the first I have seen it.

 

I was pleasantly surprised as well when I noticed the two compartments. The empty one is just big enough to fit my smokes so as to hide them from the wife!

 

Boot? Isn't that the trunk? Bonnet is the hood!

 

Yes, there are two small compartment in the trunk of the X350. One of the covers has spair fuses for the Rear Power Distribution.