After many hours of shifting games around, cloning disks, deleting partitions, recreating partitions and restoring data, I finally finished. Who the hell has 4 steam libraries across 4 different disks and 5 partitions all dedicated to games? ...Me.
Cable management took a few hours too, but it was worth it. I can definitely see the huge advantage to M.2 now. The removal of a whole drive bay along with 3 hard disks has removed 2.5Kg of weight, improved airflow through from the front and best of all, it's stopped the vibrations from the hard disks transmitting through to the case.
I finally found my spare LED for the reservoir whilst hunting for a molex to sata power adaptor. (that's fantastically hidden behind the samsung ssd so you'd never know it was there) It does look like a chaotic light-fest in there