Rambling Sid was Round the Horne, but yes, the cast were mostly from Beyond Our Ken. The origin of Rambling Sid was supposed to have been script writer Marty Feldman's intense dislike of folk music. Hugh Paddick was the other half of Sandy & Julian. (He appeared in one episode of Blackadder, as an ageing Thesbian.)

PS Re Polari - The word Camp is supposed to be of Polari origin. I thought it was Vader your eke (Ec = Ecaf = backslang for face. Also the origin of YOB is backslang for BOY!)