Problem solved.
The confusing issue was that there were 2 HM generic profiles for Pro2000 still showing in PPL when I had deleted them from everywhere I could find. But the 2 new HM generic profiles for Pro2100 that I downloaded to the ColorSync folders were
not showing in the dropdown list - still just the Pro2000 . Hence my assumption that I wasn't able to add new profiles or delete old ones.
Well it turns out that the file name (by HM) is incorrect (or maybe the file itself is incorrect) and, although they (hopefully)
are profiles for the Pro2100, they come up as Pro 2000 in the PPL dropdown list.
I finally found this out by looking at the filenames in ColorSync Utility and seeing that their description and filename don't match. See screenshot.
I'm also a little chastened by my lack of understanding of the way this software is picking up the necessary ICC profiles. I had wrongly assumed that they were all in one place but now understand (I think) that it identifies and picks up the relevant Pro2100 files from several locations.
So many thanks to Dave and digitaldog for helping and steering me to the right places to get this sorted.
Now all I have to do is find out whether the HM profile is actually the right one for the 2100.
Paul.