On the dwg I posted you will see the EARTH is used, connect the E wire to the bolt/screw which fixes the transformer to the psu chassis.
Have you got the mating IEC wired cable socket to suit the chassis mount connector you have bought.?
On the back of the chassis connector 'N' goes to one of the wires on the transformer primary, the 'L' on the connector goes to the other transformer primary winding.
As its a double pole switch I would have thought the 'N' would be internally switched on the connector.
The only thing connected internally is the fuse to 'L'. The switch is just in the same casing. You could think of it as being completely separate (as if I bought it as a separate component).
I don't have a complete chassis yet, as I want to try it on the breadboard first. Should I wire the Earth to the metal casing of the transformer for now?
I don't understand what you mean about the 'mating IEC wired cable socket', etc...