Gerard, perhaps you are also thinking of 'The Dream of Olwen', (From the film "The Way to the Stars") composed by Charles Williams, who also, incidentally, composed the music for 'Dick Barton Special Agent!'

You will no doubt be interested to know that "The Isle Of Innisfree" is indeed known as "The Dream of Alwyn", at least in North America, as the following websites (and many more sites, if you do a Google search) attest:

www.contemplator.com/tunebook/irshmidi.htm

www.worldfolksong.com/songbook/extra/heal.htm

www.racine.ra.it/ungaretti/ireland/music/irshmenu.htm

The question is still, why the connection, as it's obviously a surprise to you, too.