Can I get by using free transit visa?

I am a UK passport holder. I have 2 flights going into China.

Leg 1
- UK to Shanghai (19 Dec 8am) to Bangkok (20 Dec at 8pm)- will be in Shanghai for 36 hours
Leg 2
- Vietnam to Guangzhou (26 Dec 10am) to Bangkok (28 Dec 10am) - will be in Guangzhou for 48 hours. But also wanted to take a train from Guangzhou to Shenzen on 27 Dec.

Are each of these legs treated separately by China? And will I be able to take up the free transit visas each tiime?