Green’s Dictionary of Slang

bangers (and mash) n.

an act of urination.

1975		D. Nobbs Fall and Rise of Reginald Perrin (1976) 57: ‘Where are you going?’ said Reggie. ‘For a bangers [...] Bangers and mash. Slash.’.
1998		R. Puxley Fresh Rabbit.
2003		B. Dark Dirty Cockney Rhy. Sl.