Depends on the age of the car. Is it 1995 and after? (bubble shape). If it is...then open the boot and take out the small balck plastic clips that hold the material on the inside of the boot directly behind the light cluster. Carefully pull the material away and undo the 3 nuts that are holding the light cluster on the car. Disconnect the electrics by unclipping them where both sets of wires meet. The clusters should now just pull out from the outside of the car.
Jon, February 2008
the trim panel must be removed this is held by several clips you push in the centre of the clip and it pops free the bulb unit is held by two clips that push to one side