To get into it you need to remove the inner trim inside the boot, on the roof part under the spoiler.
You'll notice three rubber covers over very small studs with nuts.
Remove the rubber covers and carefully back off the nuts, the studs are not held in strongly and being careful here save pain later.
With the nuts backed out all thats holding this on now is the electrical lead. This needs fed through the inner boot trim to free it off.
To remove the light from the spoiler remove the two pieces of tape and you'll notice, with a torch two retaining screws, back these off and your light is free.