If, on the Browse tab in MyMpd, I change from Database to Filesystem then I can add albums to the queue with no problem at all :-)
This confirms the problem is in the database/cover view.
Further, if in Database view I select a genre then an album from it all the albums in that genre are added to the queue and not the whole database..
Need to find what database MyMPD uses and any reset command or alternatively if the problem lies with mpd as I see that MyMpd settings screen reports that the mpd version is out of date. If the way mpd administers its database is not aligned with MyMpd version then this might explain things.
And therein is found the fix!!
Seems that MyMPD and MPD versions have to be aligned. Changing to mpd 23.5 has removed the problem.
I had mpd 21.5 as I preferred that version but in the interests of use I suppose I will have to forgo that and accept the latest version.
Something to bear in mind for the future.
(Thanks @cpcat for your screenshot...after much too much head-scratching I finally looked very closely at it and the answer became obvious. lol