If the above transcription weren't accurate, I suppose Bob would have said so when he posted here. Therefore I present the following version as evidence that the folk process has been to work on his song. Copied from FolkSongCollector.com, which also has the sheet music.

WEB OF BIRDSONG
Bob Coltman

If you will weave me a web of birdsong from the thrush or the linnet,
Then you shall have my heart and hand and all the love there's in it.
If you will weave me a scallop shell as purple as the violets in May,
Then I'll be yours, and only yours, and never go away.

If you will weave me a green grass basket to carry our heart's love in,
Then you shall have my heart and hand to lock with a silver pin,
If you will make me a cloak of kisses for cover on a rainy day,
Then I'll be yours, and only yours, and never go away.

If you will love me more than fully, and longer than forever,
Then we two shall married be with a knot that none can sever.
If you will love me in the night, and love me in the day,
Then I'll be yours, and only yours, and never go away.

If you will bear me the child of our dreams and raise him to be a man,
Then I will love you more than fully, and much more than I can,
If you will bear me a cobweb child that lives unto the day,
Then I'll be yours, and only yours, and never go away.

If you will build me a bonny, bonny boat to sail on the water so wide,
Then we will sail the seas of love, and you shall ride inside.
If you will build me a house of moonbeams that lasts unto the day,
Then I'll be yours, and only yours, and never go away.