My mate Iarf sings this one , uses melodeon as accompaniment. He tells me that he see's the meanings to the verses as follows.

First verse describes him telling his love that he is going to Flandyke. (where is Flandyke?)

Second verse could be going to her bedroom for the first time and seeing her physically unclothed as in "saw a light springing from her clothes"..bit vague but understandable. The line "just like the moring sun when first arose" could be a reference to being dazzled by her beauty. A common epithet.

Last verse is being told that she is dead (by her father) and committing suicide "hove a bullet on to fair Englands shore" (himself being the embodiment of england) "just where I thought that my own true love did lie" (in his heart.)

He shot himself in the heart upon hearing the sad news.

This is how Iarf has always imagined it.

S'a lovely song. Spot.