An update - I've switched to 'real-world' shooting, gone outside and taken some shots using a number of focal points, good & suspect...
1. Manually set the lens set to full 'out of focus', both near and far, the camera will not auto-focus. It hunts. The lens moves a little, then back to full-length, then it tries focussing again, and so on. It cycles at about 2-3 focussing attempts per second.
2. Manually move the lens focus to half way or thereabouts and all focus points snap into focus using auto in a split-second.
...Okay, some conclusions, be great if anyone else has some thoughts & recommendations please?
1. There are some focus points on my (new) D4 which DO NOT auto-focus when the lens is at full length, be that near or far (infinity), and all are repeatable.
2. Focal software gives the same results as my 'real-world' test, so looks like I can rely on the Focal results if and when consulting my dealer.
3. Using 'real-world', I can demonstrate to the dealer using the method described herein.
4. Is my 'real-world' real-world? Ie. how often does one... a) focus from either end of the lens focal range unless shooting landscapes and the like (another test perhaps), and b) use the extreme right focus points - although one does sometimes use the ones on the left showing problems.
5. Heck, it's a £5000+ camera!! On this occasion I think I can confidently say my technique is sound, although I am less convinced the camera is performing without fault.
Last point, I've managed some improvement using Focal by stopping down the lens - as I'd expect.
Sorry to keep writing, but I am somewhat concerned so all help and advice gratefully received. Thank you!