Sounds like a break in the wire or an earth fault. If you have some spare wire you could connect it to the switch and just trail it over the seats to the lights at the back. That will at least tell you if everything else is OK.
If you can't get it fixed then bury the new wire in the car under the carpets and stuff and use that. Its not ideal but it will get it working.
problem gets even stranger - put in reverse, no lights - slam drivers door and the vibration from shutting the door makes them come on - EVERY TIME. after 3 or 4 in and out of gear , lights dont work - have to slam door again - i know switch is ok and power is going to the rear and i know bulds are ok, its only just started doin this so now i am gobsmacked as to the problem, sounds like it may be a connection on the wire but where???? - car was re wired by regal for c20let + 6 speed - possible bad connection in engine bay somewhere but where????