Can I use the 72 hour visa fly from UK connecting flight Dubai to Beijing.?

my friend & I will arrive Beijing on 05/10/15 for 2 nights ,touring wall of china& Forbidden City 07/10/15 embark royal Caribbean cruise around South China Sea Disembark Singapore then fly back UK. Please advice

i forget to add my friend & myself are both Briitish nationality,holding Full British Passport
Many thanks