Yeah it's a grey area alright. For AQA, I know this, I took English Literature AS last year and and carried on to A2. For AS we had 2 separate essays on two texts ) while for A2 we had one long comparison piece. I got As in the AS essays so I pretty much recycled the two essays (70ish%) and added links and new intro/conclusion etc. So I think you'll be fine as AQA doesn't use Turn It In like unis and (if you're like me) your CW is marked by the teachers and only moderated by the exam board. Plus as you've said, there's no specific rule against it. Hope it helps!