Hello! I'm confused - I need to know which type of visa to apply for.

My girlfriend and I want to fly from South Korea to Guangzhou in February. We will stay for a few days there. Then we will take the train to Hong Kong for a week. After that we will catch the train back to Guangzhou for the return flight to Korea.

What type will we need? We are both from the UK but do we need single entry or double entry type? Or something different?
Many thanks