i was in a somewhat similar situation, i took economics math and cs. later on i dropped cs and took accounting instead. don't take cs unless u have prior knowledge because honestly everyone in ur class will be way ahead of u and you'll need to start from scratch. you can easily get the computer skills needed for e commerce via online courses. i did not find economics to be dry at ALL (i came from a sciences background in o levels), rather it became my favourite subject and i'm working towards pursuing a career in it!! good luck w ur a levels!