Travel from UK stayi3 nights in shanghai then cruise around Japan back to shaghai then fly to uk

Yes, you will be eligible for visa free transit schemes in principle. Anyway, to confirm that, here are several conditions your itinerary has to fulfill:

- Your flight from UK to Shanghai is not allowed to have any additional landings of any kind within mainland China and in Japan
- Your cruise is not allowed to have its first port of call, immediately after Shanghai, in mainland China port
- Your cruise is not allowed to have its last port of call, immediately before Shanghai, in mainland China port
- Your flight from Shanghai to UK is not allowed to have any additional landing of any kind within mainland China and in Japan

If those conditions are fulfilled, you will be perfectly eligible for 144 hour visa free transit during your first stop in Shanghai and for 24 hour visa free transit during your second stop in Shanghai. In case if your entire stay will be longer than 24 hours even during your second stop in Shanghai, you will be automatically eligible for 144 hour visa free transit.