Sounds like you’ve almost got it covered @johnbanks .
Here’s a link to a NAS (Network Attached Storage) implementation I took on if it helps. emonCMS backup example to NAS network drive - #4 by danbates .
@borpin’s rsync suggestion on post 5 is interesting, I’ve not had a go at it yet.
There are cloud options too, I’ve heard dropbox is a good one on the rPi, not used it though.
All the best.