Following a hearty meal of crow with a side order of humble pie and a good night's sleep, I have now, correctly, completed this so thanks to Vagans for a truly wonderful puzzle.
I really pulled out all the stops in regards the highlighting and framing of the page in question, As some of you may know, I draw out my grids on white A4 paper which, I think, improves it as a visual spectacle - it doesn't compare with the original, of course, and modesty prevents me from going overboard but I will say that it's strikingly beautiful and one of my best yet (modestly put Brendan)😀
Massive thanks also to Drxx, Malone, Spoffy and Buddy for so patiently and politely putting up with my, at times, delusional rantings and to Jack for the sentiments expressed in @42.
After a practice run last night, I'm now off to collect my neighbours dog who I'll be looking after for the next 10 days - poor Bailey, he has no idea what he's in for 😂
... I wonder if my friend has pet insurance 🤔