Agreed, I typically plan to arrive LHR 2 hours before departure (maybe slightly less) and if there aren't any transport or security issues then I still have a goldilocks amount of time (not too much, not too little) to grab a bite/drink in the lounge. I sometimes flex this depending on the specific timing of my flight, e.g., for a 12pm departure I don't really need to eat beforehand, but for a 1-3pm departure I would probably be too hungry to wait until the regular onboard meal service unless I had a big breakfast earlier that morning.