You might not need as much exposure as your meter might suggest as it is trying to translate the scene into an 18% grey average daylight scene whereas you actually want it darker. i.e. to look like night time.
This. If you want a dark nighttime look you probably should underexpose according to your meter. I've shot 200 at night with a f1.8 lens and not had too many problems. Autofocus is pretty much useless though... For B/W I like the look of Neopan 400 or TriX at 1600 anyway.