I ended up buying the Elite version of DxO's Photolab, as it has noise reduction and something else that I'll probably never use.
It seems to work quite well at limiting chroma noise, from the two or three images I've tested it on.
Only thing I haven't yet found is if you can selectively use NR on an image, rather than a wholesale global application of it.

But DxO have or are integrating those Nik things into Photolab .. or something to that effect.
(not really into 'plugins' per se .. so I'm not too sure what and how they all work in relation to the base software).