Who is Billy's Gang from Welcome to the Monkey House and what is their importance?

Billy's gang consists of eight men and women, with their faces hidden with stockings. The women are former Suicide Hostesses. The gang takes Nancy to bed and gives her a shot of what they call "truth serum," which makes her sleep. She wakes up a nothinghead, no longer under the influence of the ethical birth control pills. The women then bathe and clothe Nancy and take her to meet Billy the Poet. The gang returns finally to hold Nancy down while Billy deflowers her and then to help her to bed.