Hmph.
The thing with English Literature though, is that the answer is so subjective. There is no right or wrong answer, so it depends entirely on whether or not the examiner agrees with your writing. Unfortunately, subjects like English Literature is a little like playing Russian roulette; you win some, you lose some.
And the really ****ty thing is, once an examiner has marked it, they don't really like changing the grade because it looks rather unprofessional (someone is basically telling another education authoritative that they're wrong...). I've been through exactly what you're going through; I sat an exam, got the perfect question (literally did the same-ish question 2 days before as a mock and got an A*) yet was graded a C. I had it remarked and I gained a grand total of two marks.
It's not helpful I know, and I'm really sorry it's happened to you. But it's the ****ty thing about doing a subjective course; some examiners simply won't like the way you write, so all your points will be considered inferior.
If it's any consolation, last year I got an A in my coursework and unfortunately a C in my exam (my teachers were furious about it, they said they would have marked the paper as an A/A*). I lost hope and just resigned my fate to getting a B over all, but this year I achieved really high A's in both my exam and my coursework and have an A over all. So it's still possible to get an A overall despite the disappointing AS exam grade!
Good luck!