The way these threads always follow the same pattern is so boring.
Some people think they should strictly follow the airline request to not take food and drink from the lounge and that's fine.
Some people still take stuff. Probably that's fine too. The airline could take more extreme measures if this was perceived as a significant problem, and they haven't.
Ultimately, BA hasn't asked anyone to act as their beer can police, so I don't understand why so many here do that.