One is in the boot itself, directly behind the light. There is a flap in the boot material. Lift back the flap and you will see the bolt.
At the top of the light, there is another bolt. If you look where the rear seatbelt is mounted at the top, there is a plastic cover on the trim just behind it. Remove this cover to reveal the bolt.
Undo both of the bolts, and then the light cluster simply comes away from the car. The bulb holder then simply unclips from the back of the light cluster!