Yes, they might have a shuffle and use a different airframe so delay might reduce or be non existent. Whilst not so much an issue at LHR outstations May only have check in for say the 3hrs before a flight. If your flight is delayed and you turn up 2 hrs before new ETA there could be no check in desks. I’d be inclined to see if you can get a global office to clarify but I reckon they will still say arrive on time and if ur now going at 1430 arrive at 6.45am