Thanks for the advice,
How would I:
"Try grounding the circuit on a body part and see if the light works. If it does, then splice a new ground wire before the harness bend at the trunk (boot) lid hinge"
I am really weak when it comes to electronics of any type. I am looking forward to tackling this problem and getting the better of it. Will give me confidence going forward.
I'd hate to think this little light can the better of me.