empty compartment?

I recently bought a 99 range rover se 4.0 and love it. However, while fixing and checking minor issues that the previous owner didn't bother with I discovered an empty black plastic container directly behind the battery. It has a disconected wire harness next to it and to spots where it appears that the top should bolt on, if it was still there.
 
I have no idea what this is? if anyone could help me I would greatly apreciate it. Oh, and anyone one know a good site to order parts from? I have a few small pieces I would like to get back up and functional.
 
Thanks,

If I remember right, that held a computer housing for a certain system...I'll see if I can look it up..

As for parts, Atlantic British is a great one, so is Rovers North (my dealer referred me to them), and Rover Cannibal can sometimes have good deals, but their stock will rotate.

And welcome to the site!

It looked like the compartment could have been for the Navigation system, but it seemed like an odd spot. Thanks for the websites I am going to check them out tonight.