Hi I can clear it up.
Originally the heatsinks were live as they were connected to live parts of the PCB, (soldered)
All I did in simple terms was not solder the water block to the PCB or any live point, but earthed it instead. The mosfets are not electrically connected to any part of the waterblock becuse I used the original mica shims, (which are a very good isolator, but also transfer heat well).
This was mainly for additional safety as the metal back plate of the mosfets measured earth when tested.
I never did find any reason for this "live sink" thing but whatever the PSU is still working fine a year on. I've done a few developments, one to help cool a coil that was getting a little hot and the other to help natural airflow, which was basically removing all unneeded plug wiring and making large cutouts in the chassis.
