Open the rear hatch, using a 10mm socket remove the 2 plastic nuts circled.
Pull the edge of the light over the bolts and swing the unit towards the outside of the car.
Pull the connector out of its socket, this can be a bit tight, keep wiggling.
The 2 clips circled can be pulled back to release the light cover.
The clip circled below can be pulled back to allow the lens to come away from the light housing.
You have now accessed the 3 bulbs, these are bayonet type that have to be twisted to be removed.
Top bulb - P21/5W
Middle bulb - PY21W (offset pins)
Bottom bulb - P21W
Cheers to Tiny for pointing this out. The plastic nuts holding the arch liner in place are the same as
the nuts used to hold the rear lights in place. If you lose one of the rear light nuts you can borrow
one from the centre of the arch liner until you get a replacement.