It's very rare for the starter line to have a fuse on it. But if you can fit a fuse that works for you, it would certainly not be a bad idea.

All power to accessory wiring it makes sense to fuse. But bare in mind most of that power comes from the alternator when the engine is running, so a fuse at the battery will only do so much.
A fuse local to the alternator would do no harm either.

All the usual places sell battery boxes of some sort, Merlin, JJC, Demon etc etc