There was a comprehensive guide to undoing them somewhere on this forum but I can't find it at the moment.
Basically, the cluster is held by a 'nut' at the back.
you need to pull off the plastic speaker grille on the shelf below the side window (held on by metal expanding clips).
This exposes a large grommet in the pillar behind the light cluster, remove this & you will see the 'nut'.
This nut is the easiest thing to drop into the nether regions of your car & the hardest part to buy from the dealer! (the guy in the parts department recommends stuffing a wadge of foam down inside to prevent losing the nut).
In the doblo toolkit is a small plastic tool and a wheelbrace. The wheelbrace can be used to slacken the nut, the small plastic tool will undo it & used to remove it (recommend a bit of blu-tac in the end of the tool).
With this removed and the two bolts, the cluster simply pulls away.