Take either further maths, a language, english, history or a science.
i would personally go for history or futher maths. your doing maths and econ, so futher maths would probably be useful and widen your career path. if not take history, its really intresting and is an essay writing subject and is very respectable.
and most importantly, do one which you enjoy .
hope this helps... : )
(waiting for the +rep LOL)