Will the 144 hour visa-free transit apply for my trip to HongKong - Shanghai - UK (where I live )?

I hold a British passport and will be flying out to Hong Kong, then Shanghai for 3 days before flying back to UK. So UK-HK-Shanghai (three days)- UK. Do I qualify for the 144 hour free transit?

The spokesperson at the official Chinese Visa Centre is adamant there is no such scheme except the 72 hour exemption. I want to be entirely sure before setting out.