The centre front overhead light does not come on at the same time as the lights in the rear dome and the foot well lights.
If I push the translucent cover it does light up so it appears that the switch is in the correct position so maybe the switch is faulty.
( my unit does not include sun / moon roof switches)

Can someone confirm the method of detaching it from the roof lining?
My first attempt was not good!!!
I attempted to pull the front edge down by sliding my fingers between the unit and the lining.
Result - one sliced finger tip. The edge of the plastic is razor sharp.
When my finger has recovered I will try again.
Is it possible to get at the switch once I have the unit removed?