LSE Social policy&Economics vs EconomicsWatch
These are my PG and IGCSE grades.
IB Predicted grades: 45/45
IGCSE: A* A A A C(lol)
If you are seriously interested in Social Policy, that is clearly the better option to serve your interests. It's worth noting though, social policy is not the same as economic policy, and there is a great deal of macroeconomics and economic policy options available in the core Economics programme. A personal statement primarily discussing economic policy for the joint honours course will probably be frowned upon if it isn't explicitly linked to social policy issues as they arise in economic policy contexts.
However, you normally take two courses outside the main discipline in the core economics course (one in each years one and two, and in exceptional circumstances with the agreement of the relevant staff, a further one in third year) in any case, so if you could cultivate some background in social policy on this programme as well as the traditional economic policy and theory options. You can also take Public Economics, a core course on the joint honours degree, in the single honours Economics course as well as the above external options.