Well I have found out quite alot about all this since I first posted.
Firstly, within Samsung Notes settings there is an option to "Import notes". From there I could import Scrapbook (there was none), Memos (47/97 only) and S Notes (apparently there are none). Suffice to say, that failed. I did lock some notes which may explain why some of them cant be downloaded but it certainly wasn't all of them!
Secondly, I knew that GDPR gives me the right to download all the data Samsung holds on me. Eventually I ended up at privacy.samsung.com which allowed me to request the download for Samsung Cloud. You can only download the whole lot (105MB for me, more if you have any media files) rather than selecting just the discontinued apps which was frustrating. Anyway, it completed today. I downloaded and extracted the files. 86 items in S-Note folder is correct but only 89/97 in K-Memo. Samsung Notes has roughly the same file size so I will presume that is OK.
The files right now need to be parsed in to something usable as S-Note are all xml files and K-Memo are .content.sync files so that will take a bit of reverse engineering. Its a start and I will update when I have finished parsing the files. I will also post any code I use to parse them with for others to use.
Hope this might help some others.