OK, managed to get rid of the hum/buzz completely! I shielded the electronics cavity, but the main issue was the input being wired incorrectly as Simon mentioned. Now the pots work as expected and really happy with the sound of the EMG H4(A)s...love the sound. Still have some slight issues with action that is really hard to rectify on the treble side but willing to put up with given the twist in the neck that i can't fix. Overall really happy with the build.

The plug and play wiring was also really cool, nice not to have to solder for a change. Need to think about next build :-)