Hi folks - I should have written earlier. I did find a translator, and this job has been completed.
By chance, in the same month, an English translation of the book concerned was published for the first time since the 18th C original publication in Latin and Old Dutch, but I did not know that a translation was under way when I made my request here.
Now I have two translations to work with, which is not a bad thing, given the many different ways that translation can be done with any particular text.
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com