interior lights!!!!

ok be kind i'm kinda new here.
i have a 200tdi on a k plate and am fixing the interior lights as they didn't work (bulbs were fine) i have run a new power feed from the battery (fused) and now the light works in the on position and only comes on when the rear passenger door is opened, none of the other door switches work. i have removed them and cleaned them up so the contact points are all nice and shiny. i have replaced the bulbs for some LED strip lights i had knocking about as they are much brighter but i can't see the LED's being the problem as they are all brand new. is there any reason only that one door switch is working? please help its driving me mental

im sure they work on ground , ie live all the time untill the switch earthes them out , gotta be bad switches / earths

It's not the switches as I have cleaned them all up and if I take the spade connector off the switch and earth it straight to the battery the light still doesn't come on. I didn't know if there might be a reason why the one door works buy not the other 4 (5door truck). There must be a point where all the door switches meet up and a common earth runs to the lights.

I have done it!!! Whoop whoop. Was a corroded earth wire in the blue plug under the dash passenger side.