Ok so I had some help from Chris (also known as 'Tesla-Chris' !) who showed me to test for voltage leakage safely, brought along a gradual voltage meter and figured out where the power blockage/failure was. It turns out the only real problem ws in the mains power supply, and it is up and running on full 220V now,- with a slight leakage into the chassis (source still to be found..)

Yay to Chris!! First device running, almost ready to be shown.