Guangzhou province for U.K. passport holder single traveller, 15 days, portuguese resident

I am residing in Portugal but still classed as a U.K. resident as I have only been here 14 months. I was planning a solo trip to Fonshan and then possibly onto Hong Kong, is there a limit to the time I can stay in either place without having to apply for a visa? I have friends in Hong Kong who could provide an invitation but not in Gungzhou or Fonshan. I could split my journey to 6 days in each place if necessary