The cheapest way to get B&W film is to buy a bulk loader and load it yourself. This isn't very hard but does add a few added problems. I'm not sure your Nikon lets you set your own film speed. Getting bulk loaded film processed may also be harder.
I like Agfa APX 100 B&W film. It is relatively cheap. Better then that it looks good to me. Supposedly the film Freestyle sells under thier own name is Ilford. I think that may be the story with Photowarehouse to.