At the moment it's hooked up like this:
US style 3 pin moulded plug, colours are Green wire is the earth comes into chassis and gets screwed onto the leg of the trans as chassis ground, then 2 black wires for the live and neutral, one black wire comes into chassis then goes to an internal plastic fuse holder the other end is one of the black primary wires on the US 115v trans.
The other black wire comes into chassis and is attached to one side of the on/off switch, the other side of the on off switch is the second black wire on the primary side of the US 115v trans...that's it. There are only 2 black wires on the Primary side.
BTW that web link you gave is the exact one i was looking at the switch looks exactly like the top one on that page except it has the 12v stamped on it.
I was going to wire mine like this