It is possible that there is some overlap with the Lomax archive tracks. Lomax recorded Bert on 17th April 1951, and Kennedy 22nd April 1951.

I understand Kennedy recorded Bert again on 12th July 1951, these recordings for BBC Sound Archive.

Trees Grow High / Cruel Brothers (pt.1) [BBC Lib no. 16418, 1951]
Royal Duke of Grantham / Cruel Brothers (pt.2) [BBC Lib no. 16419, 1951]
Grand Conversation on Napoleon / Christ did Me Ransom / Captain's Apprentice [BBC Lib no. 16420, 1951]
Polly Vaughan / Lord Bateman [BBC Lib no. 16421, 1951]

I think the CE Polly Vaughan (Molly Bawn) T3359R01 is from July, but the rest from 17th April.