It's kind of weird though. The microswitch in the lock tells the body computer to "switch on the the light". There's nothing direct and simple about it.
A lot of people have found a problem with a diode which is actually in the wiring loom in the boot area near to the wheel arch going to the boot light. If the diode breaks down and goes open circuit then there's no power going to the boot light ever.
My boot light went a year ago, and I had the same non-light that you describe - the bulb itself is in working condition, but doesn't get any current. The issue was examined by Fiat when it was serviced earlier this summer. They said it was inside the lock itself, and refused to change it for me as it would be a very expensive fix just for a bulb. Nice to know I won't have any insane surprises after a main service.
There has propably been an olympic game in having as much wires as possible back at the arches, so finding the right ones are tricky. I really didn't care, and put a small flashlight in one of the compartments above in the interior trim above the arches.
Thanks very much guys. Once again Deckchair your fountain of knowledge spews forth like a mighty..............fountain!
Weather premitting i'll try this out tommorrow. If all else fails may just make it like it should be - open boot, make a switch, light goes on.