Hey,
At A-levels, Business and Econ are seen as 2 separate subjects, but taking them together is not usually recommended. Content-wise, they are similar to some degree, so some teachers have said that it may be easy to confuse Econ content with business content.
Considering that you want to do Econ at uni, then business is not necessary at all. Also, doing 4 A-levels is considerably harder than doing 3, and most of the time unnecessary (since you only need 3 for any uni). It is better to focus more time on doing 3 A-levels to a better level than doing 4 and possibly compromising your grades.