BA serve a full evening meal in J and F on every evening departure not specifically marketed as "sleeper service", no matter how late the departure. This is in contrast to some other airlines (CX!) who don't serve a full meal on very late departures even in F. BA are actually quite good in this respect. Sleeper Service only applies to seats in Club on flights from US East Coast and a couple of Arabian places, where the flight time is rather short for meal, sleep, meal.

All longer flights also receive a full breakfast in both J and F. If you are in F, you can ask the crew to keep items for you until later if you want to sleep, wake up, eat (and optionally watch IFE or something and then eat more).

If you have a choice of routing from east Asia, I can recommend doing a daytime flight from somewhere like HND to LHR for maximal F experience.