I love the Ron Grainer score of Robert and Elizabeth and own cast albums of the '64 original with the glorious June Bronhill and the '87 revival. I've never seen a production and hope that it will eventually get a Mufti revival.
I agree about The Good Companions. The original '74 cast recording with John Mills and Judi Dench just oozes with charm. Mercer was such a quintessential American songwriter but really captured British sensibility with his lyrics for Previn's fine score. I particularly enjoy Mills' rendition of "Ta Luv".