Thanks again for all the people who answered re. the above song. I love the Scottish version. Regarding Fred McCormick's query about the distribution, I quote from the BIRDS OF BRITIAN AND IRELAND:

Although there is one record of a bird in song in Ireland and a handful in Scotland nightingales have not bred in either country.
A hundred years ago the birds bred mainly south and east of the line from the Wash to the Severn. The strongholds now are Sussex, Kent, Essex and Suffolk.

I have not quoted the complete piece but they end it with the caveat-at present there is a very worrying loss from many areas.
But then again, when the song was written they may have been all over the place including Berkeley Square. Who knows?
Maybe someone with bird knowledge will enlighten me!
Tanners