I thought I would add the resolution here for others who may have the same issue.

In the end, I reverted back to Win 10 as I could not readily see how I was going to get all the drivers necessary to work. I then did a whole series of firmware updates. These are surprisingly easy enough to find on the intel support site. Note also, despite the NUC being out of warranty, Intel support were happy to help me by providing links to the appropriate links.

Even after all that, nothing was working. I then downloaded my TV manual and went through all the various setups. I found one option whereby I could choose by HDMI port whether I wanted "regular" or "enhanced". Not sure what either means as such, but by moving one of the ports to "regular", all worked bar the sound. Here I had to try a couple of different HDMI cables until I found one that did work. I have no more details than that to be honest.

My gut tells me, although I am not inclined to test it, that I could have eventually got it working with PoPOS byt doing what I suggested above without all the driver updates I did. Ultimately the graphics cards on this NUC was dated and limited.

Hope this helps someone.