Can I use the 72 hrs free visa?

Hi. I just arrive in SHA from UK on normal business visa. I have return flight to Uk from pudong in 2.5 weeks time.
I am British UK passport holder. This weekend I need to take a trip to Myanmar. However I need to fly back to SHA to get my flight back to UK, but I don't have any visa left as just used last one entering today. I would need to fly SHA/HK/Yangon. As I am visiting Myanmar on separate ticket to my UK return....would I be able to 72hr transit in SHA on return!?