These may or may not be connected..
When I got in the car this evening, it started fine, but no life from the instrument panel, climate panel, drivers seat, main interior light, boot light.. Turns out fuse 12 was blown. Being an optimist I replaced it (ignition off, everything switched off apart from the drivers door was open) - there was a decent flash and it blew again.
As I was scratching my head, I noticed that the rear passenger reading light (the one near the grab handle) was glowing - as if on half power. On checking, both rear doors' lights are behaving strangely. With the switch in the centre position, they should be off permanently according to the handbook. What actually happens is with the rear door shut, both the reading light and the kerb light 'glow'. When the door is opened, the reading light goes out and the kerb light goes to full brilliance. Both doors behave the same way. With the switch either to the front (should be door controlled) or rear (should be on permanently), they never come on.
I think there must be a short/open somewhere, but whether this is related to the fuse 12 issue (which is the biggy - the car runs fine, but with no instruments its undrivable) I don't know.
I have a limited supply of 20A fuses but will try removing all the rear bulbs - I don't use them, so if that is a quick fix, that's fine. Somehow I doubt it though.
Any other thoughts appreciated

(The car has not been worked on recently or significantly at all. Its a 98 Elite saloon)