Thanks for the suggestion, Freddy. But it looks like it won't be necessary! Ceri Rhys Matthews from the band got back to me last night and sent the following email - also included were photos of the lyrics in a songbook:

"there are two versions of this song from cardiganshire we sing & i guess the one we recorded is an amalgam of the two. the tune we use is the north cardiganshire version as sung by thomas rowlands of lledrod, aberystwyth to a collector in the 1960s. the remainder of the words we sing come from south cardiganshire & were collected by j ffos davies in the 1920s. i'm ashamed to say i can't remember the name of the singer off hand"

Today, she also emailed:

"the other singer who sings a different version - the one i couldn't recall last night - is thomas herbert of tangaer, cribyn, near llambed. he had an amazing & unique repertoire, even among the richness of cardiganshire song. he called the song y bobl dwyllodrus - the deceitful people. we sing his version too. here is j ffos davies' sol-fah notation..." (Photos of a handwritten document were attached)

Thanks for your comment, Jim. It encouraged me to just take the most straightforward solution and contact Fernhill - without it, I'd have been too shy to take the step.