There comes a point where courtesy reaches its limits and no matter what you bring there is a risk of offending someone. Until which time the cabin crew admonishes me about the impact of my take-away food I'm probably not going to be all that troubled by the opinions of other passengers. If I can buy it on the airside then I'm fully prepared to bring it on the aircraft. At Heathrow that would include, depending on the terminal, chicken curry, miso and shimeji ramen, a hamper of caviar and smoked fish among other pungent delights.