You could retake the whole year? My son went from Bs and Cs to As doing that, better than resitting some modules. Pulling up over a grade from AS to A2 in the one year is really hard, you have a limited amount of marks available to do it in, and resits alongside A2 are going to be tough as well. Only you know how hard (or effectively) you worked to get what you did.
Chemistry is a lot of content. How were you on physics? If you were any better at that at GCSE, had physics maths and biology, all of engineering is open to you, and at one end that it quite lab-sciencey. Good results needed, but great jobs and pay at the other end.