@SimonR Thanks. Iirc that NVR you bored is available at Ali. That would probably need to be the source. I did read that the I version, rather than the K, is also still very much supported firmware wise. Perhaps they both are, but, and you filled in the detail really well, the spec is that much better, in a meaningful way.
I am deliberating as I have to consider the actual risk and the difference a new NVR and cameras would bring over what I have already. It is the difference we would be paying for.
We have had two events over a couple of decades, first whilst we had Hikvision analogue CCTV, where the recorded material resulted in the scrotes capture and successful prosecution. The second not too long after moving to 1080p.
Since the HD versions of the cameras, with floodlights, are most visible, that in itself seems to have helped. Well at least we have had no more scrote visitors.
Thanks again.