If you beat him to within an inch of his life you'll get done for ABH and get years for it, because when the cops come you won't have a leg to stand on because he was stealing drugs from YOU. YOUR illegal drugs. What im trying to say is... beat him behind the knees (back of the legs if u know where i mean?) with a bat or something so he falls, then get a relatively thin, worn out pillow and punch him through that - no marks.
DS