Everyman Belsize Park
It's an outpost of a small, boutique (and expensive) cinema chain. It used to be known as the Screen On The Hill.
An anonymous visitor (April 2009) tells us that the bar has "Space Odyssey-esque decor", and that the screening lounge has reclining seats, each with its own little side table. Our anonymous friend adds that there's table service to the whole auditorium (a "good cocktail list" plus a "deli selection" of goats cheese tart, stuffed chillies, etc) — this runs through the shorts which are played before the main feature, and stops just before the main feature screens.