thank you Bob
the culmination of my research re this song has determined that
it's not quite 'Star of County Down' but more 'Summertime' a version of which can be found by the Chieftains and is possibly a Carolan or O'Carolan tune but is at least of that vintage and is mostly known by its Gaelic title.

my version of lyrics with above mentioned tune:
http://youtu.be/rPBUNxgJikM

Graham Dodsworth