I'm sure they'll get the bums on seats, but London to Bangkok is (pre-covid) one of the most competitive routes in the world with trashed yields to match. Not sure I'd be in a hurry to fly on a 329 seat 788 either. For comparison, Norwegian had 291 seats on their 788s, and TUI had 325 seats in an all economy short haul configuration for Summer pre-Covid.
A good addition for Gatwick though, I hope it works for them.
A few other dates for long haul restarts in the coming month or so:
13NOV: Punta Cana (TUI)
15NOV: Tampa (BA)
19NOV: Orlando (BA)
24NOV: Liberia (TUI)
25NOV: Puerto Vallarta (TUI)
09DEC: Doha, San Jose, Punta Cana (BA)
10DEC: Dubai (EK)
17DEC: Phuket (TUI)
18DEC: Goa (TUI)