MM:

1) As asked above, "What equipment is on the circuit supplied via Fuse C?"
2) Connector X18 typically is in the interior/tail lamp circuits. In LHD cars it is located above the left footwell. Is your RHD wiring a mirror image of LHD?
X18 is a 12-pin connector; the two sections can be separated at the center seam by prying with thin screwdriver blades.
3) X30 is a connector for special equipment.