So it seems there is/was a maximum number of playlists which could be displayed in the Spotify Integration UI? In my cased 37. I deleted a few old 'lists (in the Spotify app) then the newer Playlists are shown at the top of the HA Spotify UI.
This limit doesn’t seem to apply to Tracks, Artists, Recently Played etc. etc… only the Playlist section.
Anyhow, fixed enough for me to move on 