Q: I am travelling from London to Shanghai on a single-entry F visa. 

My return flight includes an extended layover in Haikou of more than 24 hours. 

Will I be able to leave Haikou airport on my current visa and re-enter for my Haikou-London flight?

A: Based on your described itinerary, you can freely travel within China after entering on your F visa, including leaving Haikou airport during your extended layover. 

Source: Shanghai General Station of Immigration Inspection