from my notebook:

Carlene Carter appeared on RD & Friends on 1980-08-24
Eric Bogle appeared on 1980-07-27 & 1980-10-05
John Kirkpatrick 1979-12-30
Loudon Wainwright on 1979-11-18 & 1980-11-30
Martin Carthy on 1979-10-28, 1980-01-27 & 1981-02-xx
Michael Chapman on 1981-12-13 & 1983-03-20
Richard & Linda Thompson on 1980-12-07 & 1980-06-22