How to obtain 72-hours visa-free transit for Kunming

Hi there, I have a flight from HK to KTM with a 19 hour layer over in Kunming. I will be travelling on a UK passport, I am just wondering how I apply for a 72-hours free transit as I want to visit my friend who lives in Kunming City. I am currently in China at the moment and have been for the past 2 months, can I apply for free transit in Hong Kong or even in ? Any advice would be great!