I got a half day.  That is what I asked for.  I got it alone too.  It's well worth it.  I was going from a 4 door saloon so needed to be sure I could cope!  Got an S2000 too, got a half day accompanied.  The sales girl was hot and really nice too.  She didn't try to sell it as I knew more about it than her.    
  
Ask in advance to book an extended test drive.  If the Nissan dealer won't let you then call NMGB and ask them.