One of the best versions of Bedlam Boys was done by the Cecil Sharp House Choir, Sally Davies arranged it in a fine round in the chorus - but CSH won't allow her to record anything, which is more than just a pity.
I would also suggest that if you don't take Long Lankin as possession, then it must be about psychopathic madness. You could also probably treat the entire ghost corpus as displaced grief, verging on schizophrenia.