Have you reprogrammed the key fob?
The central locking are on the same circuit as the courtesy lights, so it sounds like a wiring/fuse problem
Sorry to sound patronising but are you sure you've checked the correct fuses?
Also maybe worth unplugging the courtesy/interior lights and then try (take off the casing and pull out the light. Then unplug)
The fuses aren't in either of the main fuse cluster, they're until the driver footwell, above the pedals, just to the right if the steering column...
(Added later - if it is a dodgy interor light, its usually the one in the back not in the cab)