Jon: if you can supply MacColl's own transcription, that would be very helpful. I have no quarrel with "the folk process" in its genuine manifestations, but an inaccurate transcription of a commercial recording is another matter entirely, and needs to be accurate if it is to be of any use as a reference.

Going to the broom could very well be euphemistic in this context, though I doubt any connection with "jumping the broom". It's perhaps worth mentioning that the often-debated phrase lay the bent to the bonny broom, though often interpreted as some sort of herb-magic, is at least, if not more, likely to be a sexual metaphor; though I don't think that it's necessary to look for a metaphoric intent in this particular case.