if you do biology chem phys maths further maths you can go into basically anything sciency you want (medicine, maths, engineering, natural science, a pure science subject, economics, etc). you don't need economics to do an economics degree, and i don't think you need computing to do computer science (but it might help). if you take economics/computing, you'll basically be shutting yourself off from any type of biological/medicine type career, but if you're sure you don't want to do medicine etc then that's fine.
so essentially if you think you might want to do medicine or biological natural sciences, take biology. if not, then just choose whatever you prefer.
i took 5 then dropped to 4 because i decided what i wanted to do halfway through the year, and taking 5 at first is good because you can see what you enjoy, choose a university degree, then potentially drop a subject that you don't need anymore. i doubt you'll need to continue all 5 for the whole two years, so i would recommend dropping one of them once youve decided what you want to do.