Originally Posted by corporate-wage-slave

Not exactly, it's all about your Ready To Fly record, which is an integrated record system that handles passenger services such as boarding. As mentioned in my earlier reply you may have to visit the Visa Check desk on your return, but so long as the agent properly dealt with you at the service desk, even that should not be needed - you would just scan your boarding pass to enter Departures airside. If you have checked luggage I would nevertheless enquire about that when you return to the lounge for the second time.

If you use the transit then there is a definite piece of work to get you airside again, it's not a check-in exactly, it's about getting Ready to Fly back in line, but it may require an experienced agent to sort you out (one wearing a blue name tag rather than a silver one).