My interior lights dont work in my cab or in the back of my transit?

I have a 2001 swb transit van and my interior lights do not work inside the cab or even the lights in the back.
I found a fuse board with relays under the bonnet and looked at the fuses but found they were ok. They stopped working after i loaded a matress in the back and knocked the light out of its slot. Any one have any idea please

David Biggs
January 2008