So I've been learning lots and getting better at blender. Today I learned about linked objects, and after much research managed to get them to behave as desired using groups.
I'm working on creating a model for the engine for a light cycle, based off this image: http://www.filmedge.net/Tron/hello/SP_lightcycle_engine.jpg
I created two .blend files, one for the basic shape, and the second for the "fins" (the repeated angled blue bits that go from left to right). As you can see this one object is repeated lots, so using linked objects / groups makes sense. By my reckoning there should be 12 of these around the central cylinder. Which means they should be placed at 30 degree angles around the outside.
Googling suggests that you can use the spin dup tool, however that needs to be in edit mode, and because I'm using linked groups, I can't get into edit mode for that. I also read about the mirror modifier, but you can't apply modifies to linked groups either.
Is there a way to do this automatically?
EDIT: I've been reading about pivot points, which would at least let me duplicate the group and manually rotate around the correct centre. Except you can't set the pivot point of a linked group.