Thanks Bruce.
That doesn't work for me because when I go to "storage" it shows 560MB
in"messages" but then when I go there I see.... photos/videos/gifs =
less than 1 MB in total and "Other" = 588 MB! I click other and there
is nothing listed in there at all :-(
HOWEVER.... I tried the same on the Mac and... General > Messages >
click the "i" button... and Voila... there they all are stored in
various locations on the Mac HD - hence (I am guessing) the reason they
are not visible on the phone.
Gone through and deleted the unwanted ones and recovered >300MB
So thanks for the pointer
JohnB