So what have I messed up and where to check?
 

After messing around swapping the "temperamental" interior rear light unit I went into the car just now and nothing works.:Confused:
No interior lighting front or back, no footwell lights, no puddle lights, no map lights, no sun visor lights. Boot lighting is OK.

Nighttime/background lighting comes on OK so it's "just" the cabin courtesy lighting that's failed. Is there a fuse or controller somewhere to check?

Have you tried switching the ignition on and off again? Could be if the lights were on a long time or doors open that its gone into battery saving mode. Mine does this when Kai manages to reach a rear map reading light while I'm getting him out of the car and don't notice!

Give that man a medal. +++

One of the iffy rear reading lights was indeed switched on. :Confused:

Cool - glad that was easily sorted without much head scratching!!