3U 8205 then CZ 303 at Guangzhou
Kunming → Guangzhou → London Heathrow
Timetable, Guangzhou time
19:503U 8205 from Kunming at the gate
13:50CZ 303 to London Heathrow leaves the gate
18 h apart on the timetable, overnight
CZ 303 leaves 18 h after 3U 8205 arrives on the timetable: more than half a day, so not a connection we count.