Hi Harm,
Well and indeed! Using this technique solves the problem. Thank you. Curiously, I make heavy use of this in my scores, but just could not see my way around it in this instance.
Image of exact solution attached. The crux of it is the transition between up and down beaming where you can just say something like this for the d-sharp in question:
\once \override Stem.beaming = #'((0 1 2) . (14 15 16)) dis'''32
For anybody who comes across this matter in the future, my example code is attached - a bit too involved to be an MWE I am afraid.
Gratitude to all for helping with this one!
Andrew