Good luck - but if you are stopped and charged more, please don't take it out on the staff, none are directly employed by any *A carrier and they are no doubt all on the minimum wage in exchange for long hours but if boarding is slow it's no doubt they who get it in the neck.
On a positive, you will get a choice of four lounges all of which are above average, T2 is the best of the LHR terminals by a long way and there are many good things about the experience including a pretty fast Gold Track.