OK, others have answered a number of possible questions.
The LHR Arrivals Lounge - it's landside, on the second floor (above arrivals) via a lift. It closes at 2 PM. But if you arrive at a good time, they will press clothes, have showers, and offer a variety of breakfast foods.
Originally Posted by
ascensions
Thank you everyone for their responses, I'm learning so much.
I had no idea about the Fast Track lane, I've passed it before, but didn't know what it was. I'll definitely take advantage of that!