Hi Harm,
Many thanks for all this work, but having the noteheads centred does not help as I need to not have that - sorry, I never mentioned this aspect in the original post actually because that was not the query.
Also, when I compile this example there are whitespace gaps all over, and I can;t really deal with the 14 decimal place numbers easily. This is in no way to denigrate yours or anyone's efforts, but I am forming the conclusion this is something lilypond just cannot do.
In a case like this, I will just have to twist the arm of my composer colleague to get him to notate the section in a more conventional way but generally I only get a response when ALL technical avenues have been pursued!