Can i come back to Shanghai without a visa for 1 night?

Hi,

i am currently in Shanghai on the second stay of a double entry permit from the UK. Before I head back home, I would like to leave China for a weekend, then come back to take my (already booked) flight back to London from Shanghai. Would I be able to fly into Shanghai, stay in the centre for 1 night and then fly back the next morning even though both my visa entries have already been taken?

Thanks!