Caged animals? Unleash the narrative beast please! If ever there was a wasted opportunity to add another Great British prison movie to the roster headed by Alan Clarke’s incendiary Scum, then Screwed is it. The credentials were promising. Based on the real life memoirs of Ronnie Thompson, an ex squaddie who post a tough tour of duty joined the prison service and apparently found another kind of war on the inside, and the adaptation to screen is headed by Brit thespian bad boys Noel Clarke, Frankie Harper and James D’Arcy. Yet what unfolds for the duration of the pic is the standard raft of…