At what point would you go later to the airport?
What if the App told you it was going to be delayed for five hours? Ten hours? I realise this is rare but just making the point - do you always go for the original time even for very extended delays?
Also I don’t buy that this is a HAL issue rather than BA as it doesn’t apply to their other terminals.
I have never missed conformance as I’m more of a “enjoy the lounge” sort of person but I’d like to know what the advice is for a very long delay of several hours.