Taking the A380 will increase your chances of using A but not all A380 flights depart from A as there are A380 gates at all three concourses. 777's also use A on occasion to add to the quandry! Having said all that whichever concourse you leave from it is worth having a go at getting in to the lounge in A by turning up and being polite and saying that you just want to experience it for the first time and you will probably be let in. Just be sure to leave yourself enough time to get to your gate if you are actually leaving from one of the other concourses.