you can get your lounge voucher (at least from BA)
i passed the line at the regular check-in area (went from the side).told the security guard i already did check-in and i think even showed him my sticker on the passport (from doing the hand-luggage check-in) and told him i just need to take something from the airline desk so he let me go threw. no line at check in at BA J, took from them the voucher for Dan+.