The Child Ballad point is an interesting one. I deliberately excluded them because I thought I would go through the set separately and see which ones I reckon are still very widely known. I agree that Barbara Allan and and Lord Randall are still up there in the UK, as is The Raggle-Taggle Gypsy. The Cherry Tree Carol does well at Christmas and many people know, but few love, "Blow Away the Morning Dew" because it was a school-standard. John of Hazeldean (or more likely Jock) probably finishes the set that 90%+ of UK people know.