Firstly, the app looks excellent. I NEVER pay for apps, but this was an exception. Perfect for my needs!
Secondly, yes I used the search, but this forum won't allow you to search "D750" as there are "too many wildcards" which is very 2002 but I admire the nostalgia.
Problem is simple - open the app, hit "Nikon" it finds the camera (after a bit of encouragement the first time), hit LV, live view opens, take a shot. The app crashes.
I assume this is a simple fix and I'm just being stupid!
Thanks guys.