Despite my love of Economics, I will tell you that you don't need it for an Economics-related degree. Maths is much more important.
As for History, it does get harder, so that might be something to consider. Those were your worst grades, and at the end of the day you need to get the best grades possible. If you do drop History, all the analytical skills you get from that subject will likely be covered by English so you won't be losing out in that respect.