Cwm Rhondda, Hey! That's another song I know! At least I think so. I didn't know it was named after a girl name Rhonda, though.
The name I knew it by was "Guide me, Oh Thou Great Jehovah" {Guide me oh, Thou Great Jehovah/pilgrim through this barren land/I am weak but Thou art mighty/hold me with Thou powerful hand". The "bread of heaven" part comes in the refrain {bread of heaven, bread of heaven feed me till I want no more}.
Is this the same song you are talking about? If so, I'd vote for that one over the other ones mentioned.
But what I wanna know is what does "Rhonda" have to with this song and what does "Cwn" mean anyway?