on the outer body, rear tailgate(pre 95), rear arches,front wings,door bottoms and top of screen are the common ones
unseen body parts also rot, rear subfrane mounting area, floor to sill joint often looks ok but has festered under the sealant, outer sills usually under the door through careless jacking up.
its not a widespread problem compared to Fords etc of a similar age and i can only say it affects a small percentage of the cars we repair/strip/service.