Overhead lights in habitation area

Hi my 2008 Ford Eton Autosleeper overhead strip lights(all3) are suddenly not working. The fuses seem fine. Any ideas why they all 3 don't work?

For all three to not work there is a common failure on the 12v supply line somewhere. My 1999 Pollensa has a separate, dedicated, 'lights' switch on the main control panel and of course if that is not on, no lights will work.
Bizarrely I think, I do not have a panel of fuses as modern vans do. So I have installed one . . . . lots of wires are involved.

Often there's a master switch by the doorway that needs to be 'on' before the others work. It's easy to knock to 'off' when leaving or entering van.