I have just fitted an additional light in the boot. Just added one to the near side as is fitted as std to the off side.
Dont ask why i felt the need to do this, but i did, and can report it is very useful. In fact why did Citroen skimp in the first place?
Simply obtain the usual light fitting from the boot of a scrapped car - just rip it out from the material liner. Peel back the material liner on each side to gain access to the existing and the new light positions. Remove the boot sill trim - to hide the additional wire under (the bit across the back covering the boot catch - five screws under the little plastic pop out covers). Then just run wires between the new light and clamp onto the wires of the existing light.
Makes all the difference.
Now i'm tempted to fit a light into the arm rest cupboard - simply because i just happen to have the light and switch from a spare glove box... I'll let you know whether its worth while or not!