So here's homebrew my solution:

Fully sealed ABS box, going to use waterproof cable glands for the wire entry/exit. Has four (high-beam, low-beam, spotlight, cooling fan) 30A heavy duty chassis mount relays each individually fused via 4-gang fuse block, wire connection is via 30a screw-terminals. Everything is held in with quick-set epoxy.
Everything can be brought from Jaycar, though I did spot a nice 4-way blade fuse holder at Supercheap, could be used in place of the glass fuse holder...
All thats left for me to do is drill the holes for the cable glands, and mount/wire the thing in the car...