When to apply for gap year placements?

I have been rejected by LSE UCL and KCL for economics and all 3 rejections were because of predicted grades as it didnt meet the A*AA standard offer now i am on track to achieve A*A*A and want to reapply to the same unis.

My questions is when do i apply for gap year placements like placements in banks as i really need something to write on my personal statment. Do i apply during the semptemper october period where i will be reapplying to the unis also or shall i apply earlier?

Thanks