Is too unrealistic for me to aim for an economics course in universities such as Imperial and Warwick when my GCSE grades average at only an A? I noticed majority of people who even consider applying to such top universities are those with 6 or more A*s at GCSE and mostly all As in their ASs.
I on the other hand has disappointing results in January with 2Bs (Maths and Econ) and a C (physics, which I am retaking again in June) and I am definitely going to try and aim for 4As in June but am projecting myself maybe 2As and 2Bs at the most?
As Azland says, wait till you get your AS results first otherwise the mental stress and worries will eat you alive and make you crumble away during your exams by not being able to concentrate. And you do sound stressed.... so at least get your AS exams done before you start making options and a plan(s). Good luck.
P.S. Unless the requirements are for a specific no. of A*s, then generally, universities won't care. All that matters are your predicted A2 grades.