Interior electrics question (77 GTB)

Would just like to ask the board about something before I begin tearing into my interior: the radio is dead, the fuse at the back of it is fine. I've also noticed the courtesy light and the two lights in the doors are out. Are these two part of the same circuit or is it a coincidence? How likely is it that a short in one of the doors is stopping the radio from working? Would it be anything to do with the speakers?

Any help very much appreciated!

 

d'oh *sound of slapping forehead*

Thanks barry. I did check the fuses but not very well.