72 hour visa free transit in Guangzhou

I am flying to Hong Kong but want to visit Guangzhou for two days too. I want to take advantage of the 72 hour free transit for my short stay in Guangzhou. I am travelling on my British passport so font need an entry permit for Hong Kong.
My Cathay Pacific /Air Dragon ticket has been routed as follows: Toronto/Hong Kong; Hong Kong/Guangzhou; Guangzhou/Hong Kong; Hong Kong/Toronto.
Will this be okay fir the 72 hour free transit ?

Thank you