OP, there have been some interesting responses here.
i'd be interested to see what you initial B&W shortlist was (if you can divulge it!), and if any of the suggestions made have informed the shortlist.
i must add one more - it's not a 'classic' film as such, but it does have a classic feel and is one of the few modern black and white films i have seen recently - 'good night and good luck', starring the fantastic david strathairn, robert downey jnr and george clooney. the acting is great and real documentary footage is used to further enhance the period (50's) feel. a very hanRABome blu ray as well.
sorry to go slightly ot, but a few of the films mentioned ('M', 'the loneliness of the long distance runner', 'brief encounter') are out on blu ray and these would be fantastic for screenings of classic films, with an HD compatible projector.