University choices for Economics

I got ABC and Lancaster wanted AAB, but still accepted me and given me an unconditional offer for 2017 entry, which I am very happy about. However, I am considering reapply and retaking some papers as I feel I am better than ABC, and I would really like to go to other universities such as Exeter and Bath.

My real questions are;
Is it worth reapplying?
If so, is it worth reapplying to Lancaster as they have favourable entry requirements, especially if i mess up again and have already accepted me before?

Thanks