I remember going to Collet's in New Oxford Street about 1964 and being delighted to find the Folkways (cardboard cover) LPs of the Elliotts of Birtley and the Borders LP featuring Willie Scott et al, so they were available then.
There were also LPs on the same label of Ewan MacColl, singing the bothy ballads he'd recorded from Scottish singers. It struck me then that it would have been more acceptable if those original singers had been on the record, rather than the collector's version....