I had this same problem.............I found a dwarf in the corner tapping morse code to the outside world in a bid to gain freedom.
If it's a slight metallic rattle (like something loose in the spare wheel tool tray) it will be the lock mech attached to the boot release handle (seat badge) mine did it when i first got it. there's a thin metal rod that runs from the back of the handle to the lock mechanism, it's threaded so you can adjust the amount of travel the handle needs to open the lock. Unfortunately you need to remove the plastic boot lid cover to get to it which usually means snapping a few clips. all you have to do is wind the rod round until it takes up a bit of tension and voila.
How do you remove the boot lid? i had a look but not sure if i just need to give it a good pull or is there screws and things that need to come out?
The problem was exactly as Sheffboy explained, the boot mechanism.
You have to remove the screws in the boot handles then give the trim a good yank and it should come away. then simply wind the mechanism in.
I broke 2 clips on my trim btw but bodged it and put it back on. A new trim from the dealers, well the one in Letchworth is about £45.00
Niceone! I will give it a go at the weekend, lets hope it work?