A level choices Watch
Also taking a science A-level doesn't completely rule out economics subjects and often when you apply for science and medical degrees they prefer you to have A-level maths depending on the course.
Your best bet is talking to your teachers or if you can asking teachers wherever you want to do your alevA-le
I suggest you find the exam board you would do for chemistry and biology, and looking at what universities require for economics. You mainly need 1 or 2 required and the third and fourth are up to you.