He found fame at 18 in Caroline Aherne's sitcom, but is celebrated today for taking on Jeremy Hunt and Nigel Farage. He talks about existential angst, the death of his sister " and his 'superhero complex'Four pm, Friday afternoon in the pub, and we start with a beer. "I'm an actor, therefore a chronic narcissist," Ralf Little says. "I'm excellent at talking about myself." Seven hours later, he has proved his point.Li…