Thank you.

Sounds like it's either hotel, or take the 'normal' overnight transatlantic flight.

Does LHR have a hotel desk at arrivals where one could grab a potentially cheap last-minute hotel room? Depending on how I feel, and when I actually arrive, I may or may not want a room, primarily because after immigration, etc., by the time I'd reach the hotel it would be close to midnight (flight arrival is 2200), and I would need to be back at LHR around 0600 (for security lines plus time to roam around all of T1, as I'm an airline/travel nut).

Is T1 pretty much dead in the overnight hours, so a book might be my only activity if I decide to kill time there? (my only experiences with >6-hr transit times have been at SIN, so maybe I'm spoiled!)