2001 Peugeot Partner Rear Interior Light won't work!

Hope somebody can help. My trusty old partner van rear interior light won't work. When I bought it had to put a new switch on the drivers door as that didn't work. At same time bought a new bulb for rear courtesy light but it made no difference.
Biggest problem is I can't find where the switch/contactor is for the rear doors so that I can check the wiring for damage. Can anybody help what should be a simple task!