I'm really, really, really happy with how this one came out. It's so dramatic!!!
To cut down on repainting time, I used Levels and Curves adjustment layers to massively change the colour and lighting conditions of the characters.
Also tried to wrap my head around ACES colour management and taking that from my renderer into Photoshop - turns out PS support for it is pretty abysmal, but messing around with some LUTs helped. If anyone's got a good solution for it, please hit me up!!