First of all I have done the search but found nothing specific. I know the hold down the button trick to switch the interior lights on and off and have set it both ways i.e. on and off but whichever setting it is on the interior lights don't come on when I open the door, unlock or press the button normally.
The rear ones work off the buttons as do the front reading lamps. The door puddle lights work but the footwell lights are a no no as is the boot light. One day last week I saw that the interior lights had come on all by themselves when I was out and drawing the battery down to 10V which is when I recharged it and disabled the lights until I could sort it out. Since then I have tried the 3 second trick and got the message "interior lights on" so they should work.
I've had the light out and cleaned everything but being a pcb there isn't anything obvious. I have checked the fuse but seeing as it also covers the rear wiper and sub amp both of which are working its not that. I changed the festoon bulb too and even tried one from a breakers today. Nothing worked on that one at all. It was dated 1998 so two years older than mine.

Any ideas anyone??

Previously I have disabled the interior lights in summer time or when I am in and out the car regularly to save battery drain and it has always switched back to 'on' mode.

I'd be having a look at the driver's door lock and the microswitches inside. If that all looks good then I'd move on to the wiring from the door into the wing.

Low battery volts can cause all sorts of weird happenings in the BECM, that would be my first thought.

Update;
When the 'interior lights on' is activated the only ones that work are the door puddle lamps. All other bulbs are ok and the battery is relatively new and sits at 12.6V static and charges between 13.6 and 14.4V measured at the terminals when the engine is running.