LON-PKX transit to PEK to HND

I plan to fly with BA from London (Heathrow) 15:05 LHR on Mon 17 Jun 2024 to arrive in Beijing (Beijing Daxing Intl) at 09:35 PKX on Tue 18 Jun 2024. I need get to Beijing Capital International Airport (PEK) to pick up a flight to Tokyo Haneda Airport. Can I do this? Can I get a 72 hour visa with a UK passport?
On my return journey, its HND>PEK transit PKX>LHR