Just off the top of my head, and restricting myself to the Child ballads, I can think of quite a few that have versions with choruses or refrains of one kind or another:

#1 Riddles Wisely Expounded / Devil's Nine Questions
#2 Elfin Knight / Cambric Shirt / Scarborough Fair
#3 False Knight on the Road
#9 Fair Flower of Northumberland
#10 Two Sisters / Binnorie / Wind and Rain
#12 Lord Randal
#14 Babylon / Banks of Fordie
#16 Sheath and Knife
#17 Hind Horn
#18 Sir Lionel / Bangum and the Boar
#20 Cruel Mother

The choruses drop off quite markedly in the collection after that point, until you get to the late 200s and lighter ballads like Our Goodman (Seven Nights Drunk / Old Witchet), Farmer's Curst Wife, Jolly Beggar, Friar in the Well - several of which have 'fol de rol' choruses - and the maritime ones like High Barbary, Golden Vanity and The Mermaid, which are the kind to get a crowd of shanty singers going. Those early numbers tend to be sombre in character, and the choruses are more of a 'slow build'.