Trouble , I believe, posted the link to the ISO, A little while ago.
https://www.microsoft.com/en-us/software-download/windowsinsiderpreviewiso
It looks like, if this is the procedure from now, there is no further need to be in the insider program.
I was determined to wait for the full release, but in the end couldn't resist.
Downloaded the ISO and installed. Although I selected to keep my settings and data, it didn't to to well in that field! Not too much hassle to sort it out, though.
I also selected to check for updates, at the beginning of the institution. That might have been a mistake, with my very slow copper wire connection. Took about half hour..
From there on, up to a useable desktop, it took a further 35 minutes. A little disappointing, but absolutely no problems. A 100% success.