At this stage I moved onto my Mac and started anew on an image generated with Adobe Illustrator. This seemed to improve the development of the image and appeared to be the correct choice.
The image has now reached a kind of equilibrium and, as time is running out, I will find a digital printer to produce an inkjet edition for me. The initial quotes were surprisingly expensive so I may have to modify my expectations (a familiar process for me).
Unfortunately the print was not selected for exhibition this time. However, the process of working on it has opened up a new thread of investigation and the value of this for my work overall far outweighs participation in the mini-print exhibition.