Visa Requirements - Beijing / Chengdu

Hello,

I plan to fly from

South Korea - Beijing - Chengdu - Lisbon

Arrival | 4th May 13:35 | South Korea - Beijing
Connection | 4th May 16:50 | Beijing - Chengdu
Departure | 7th May 14:35 | Chengdu - Lisbon

I am a UK citizen.

Can you please let me know if I require a visa for this stay and if so which one.

Thank you,

Nikki