His flight lands at 21:00 UK time. It's unrealistic to sleep (non drug induced) on such a flight and there is no info here about class of service. The best thing to do is to take a nap in the morning, but the hotel is going to be a problem. You could be at the hotel as early as 6 am if you arrive at 5 am at HND and get up at 9 or 10 am, and then make sure that you stay up until the next night.

If you stay up all day as a zombie then you are likely to fall asleep too early in the evening and screw up your clock even more.