Happy to report that I received Lobster Thermidor on both flights, despite the fact that the British site showed Vegetarian hindu.
On both LHR-BKK and BKK-NRT flights, the cabin crew proactively informed me that I had Lobster but could select something different from the menu if I didn't feel like eating lobster now.
Verdict: both were good but ex-LHR was actually a bit better.