So, issue resolved, though not entirely clear why. I went into settings, and into picture settings, and switched "picture mode" to "user" and DNR noise reduction to "off". Photos now fine. What I can't figure out is that I went back in and turned the DNR back on and the photos were still fine. So something funny there. But DNR does appear to have something to do with it. Leaving it off anyway.
Had a first play around with the U22 last night (my first Android box other than a FireTv stick), and really like it, using Launcher 3 though, find the icons on the other minix launcher a bit big on the icons. Read about a few other launchers online and might play around with it. But very happy with speed of system and looking forward to adding apps and getting the most out of it.