Carole - I dont think that there IS a 'standard ' Chorus song - It varies from area to area , and even club to club ! Hovering Bob's song
'The Kestrel ' is a 'standard chorus' at Maidenhead and Herga , but has probably never been heard by a lot of Northern club Singers .
Some of Ferrera's list could well qualify over here , as would a lot of Keith Marsden , Stan Rogers , Jez Lowe , Tom Paxton , Eric Bogle , and a lot of Traditional songs popolarised by The Coppers and Young Tradition and Watersons .

By The way - What IS a Folk Song ??