Replacing Rear Number Plate Bulb

[BigD]

I need to replace one of the bulbs above the rear number plate of my C3, but have no idea how to get the cover off. The manual is no help ("Unclip lens and pull bulb holder", how do I unclip the lens?!). I've found a couple of similar threads on the forum but none of them give a detailed description of what to do. I've tried putting things in the little holes on the side of the cover, but nothing seems to happen so I'm obviously doing something wrong.

 

Please help!

[stimulator]

At each end of the lens there are two small holes, you have to insert a small screw driver into the holes to release the catch.