Glasgow-Beijing (via Dubai) Arriving 3/Oct/2019 Departing Tianjin to Japan on 7/Oct/2019

Yes, this is very good example of air to cruise itinerary that is eligible for 144 hours visa free transit. I understand that you have mentioned that you will depart from Tianjin to Japan, but you should just check your cruise route to confirm that the first port call after you depart from Tianjin is one of Japanese ports. I'm telling you this because it is not allowed, within the rules for 144 hours visa free transit, to have any mainland Chinese port call immediately after you have departed from Tianjin.

Your itinerary is eligible for 144 hours visa free transit. The only detail, you should check is to determine what port call is the first one after you leave Tianjin. This is very important detail because in case that your first port call immediately after Tianjin is any Japanese port (or South Korean), then you are fine, but in case that it is a mainland Chinese port, then you would not be eligible.