I think dirk_pumpa has it. Just back from the Man Cave after taking the Freehub apart. It was indeed pretty easy – the neighbours 7yr old daughter helped me do it!
The bearings are running fine but one of the springs is a little wonky. No idea what the pawls are supposed to look like but they weren’t obviously damaged. Cleaned everything, regressed the ratchet and put it back together. Still making the high pitched whiny sound and now with grease in it the ratchet is barely making a whisper. Time for new paws and springs I guess.
I presume if the ratchet is worn then it means a new hub body?