Rob,
I don't have a problem with Clifton's songs marginally predating the published date as he very likely sang them in public for a while before they were published. Whilst he sometimes parodied his own songs and sang songs written by others there's no evidence to suggest he ripped any texts off. His Irish stuff is well attributed to Gavan.

Do you know where we can get copies of either 'Water Cresses' originals? I will keep a good look out for them. I know where there are some stashes of Clifton sheets for sale, but they're getting a bit pricy.