This is an old post, preserved for reference.
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I added the 4mm posts and a new 'output on' LED wired across those (well almost +V is taken from the input side of the ammeter so as not to show up on there. I also removed the original 10K divider resistor from the main PCB and replaced it with one directly on the output, to remove any voltage drop from the internal wiring and the ammeter.
I replaced the faulty mains switch with a chunkier one and added a mains LED. I replaced the mains socket on the PCB with a 0.156" header to tidy up the wiring.
And now here is the finished unit, next to my existing 5V / 12V bench supply.
Note from 2022: This is still in regular use, still with the "temporary" pencil labelling.