Before I became involved in the folk scene (c1965) as such I used to obsessively listen to a wide range of radio programmes from all round the world and it's surprising how much folk music was casually being aired in the 50s and 60s, mostly by the likes of Joan Baez, Kingston Trio, Burl Ives etc, and also quite a few British people with posh voices singing folksongs such chanties. Added to this we heard in school many folksongs on programmes like Singing Together. Familiarity with a wide range of this sort of material was inevitable.