I have a confession to make. When I wired up that switch to shut off the door activated cabin lights it did not affect the additional lights (LED strips) I installed in the footwells and the step protector. Had me puzzled for a while, I thought I had connected those lights to the map light feed which I thought was the same feed that the other lights were on . The Bentley wiring diagrams didn’t help until I looked at the “after 1990” pages. Turns out that the map light gets its power from a different feed (but still protected by #3 fuse). So in order to be able to switch off those lights independently of the door switches I would either have to intercept the power feed or simply intercept the power going to #3 fuse.
This post describes how I feed the circuits on #3 fuse from my auxiliary battery. And in this post you can see how I subsequently powered the radio with its own feed. So all that was being powered on #3 fused circuit was the map light, my footlights, glove compartment light, and the cig. lighter. Easy to see that putting a switch on that circuit would do the trick. But wait you say, won’t you want to have the cig. lighter powered all the time so that you can plug in a USB charger or something? Well, yes, I suppose. I’ll see how it works out. I’m wanting to add more power points in the van, the cig. lighter may become redundant.
I went ahead and rewired the switch. Here is the updated schematic.
Addendum: cutting power to #3 fuse circuit also cuts power to the dash clock. I can live with that, I have plans to hard wire the dash cluster due to a very deteriorated instrument foil.