All 300 series (uk only) and without headlamp levelling had the dim-dip function when they left the factory until their end with the1998MY.
Dim-dip only functions when sidelights and the starter switch is turned on only, switching on main beam, dip or high will override the system
Simply disconnecting the electrical plug from the resistor in the engine bay will isolates the whole of dim-dip system.
As for fuses u did test fuse 10 & 11 in the interior fusebox, if also high beam was missing then the 30amp fuse in the engine bay would be a suspect.