I've mentioned before that I (a) don't read music, and (b) am pretty
much a beginner with LilyPond.
...
I'm really only concerned here with how to better grok LilyPond.
- For full measure rests I saw you use 'r2.' In the song of the heather. Instead use 'R2.' (capital 'R') for full measure rests.
- I'll echo David Wright's comment on using correct lyric extenders.
- In older music with lyrics it was common to see beams broken for each syllable. Today it's common practice to not do that. I'll leave it up to you to decide which style you want to follow. It sounds like you're using an older edition for a source.
-----Jay