Was good! Issues with Double Dragon and (on and off) Pac Man but plenty running and not busy, at all (12-3) so easy to play what you wanted when you wanted. TMNT (4 player), Afterburner, Robocop, OutRun, DK, Daytona, Millipede, Track & Field a mega tech, space invaders and another 10-15 I'd say. All stand up versions. Plenty of consoles and handhelds too (Gameboy, Game Gear. GBA). Consoles were N64, Gamecube, NES/SNES, Segas, PS2. Atari multigame (Flashback?) and so on all running a single game (rotated daily I believe).
Kept me and my brother busy for 3 or more hours and wanting more (got a bit "one more go" on Track and Field). £15 entry and all are freeplay.
If you're free for a few hours and in central/west London pop in. I think during the day at least you'll get in no problems.