Morwen, you are making assumptions that "Cudelia Brown" and "Day dah Light" are pre-1904, or uncollected by Jekyll.
Jekyll states that his songs are a selection, and that they varied from district to district.
Interesting line of inquiry- Is there an archive of Jekyll material somewhere?

Murray, 1952 "Folk Songs of Jamaica,"- should get to this book soon. Dunno if it has "Sly Mongoose."
It was printed in an insert dated 1949 for a Frats Quintet recording, with the title "Run Mongoose."

Your Australian libraries might have a copy of Claude McKay, 1912 reprint 1969, Songs of Jamaica. The reprint, as well as the original is rare, $125 for the only copy I found listed for sale. I don't know what songs are included.
McKay's "Constab Ballads" is very rare.