I use the BW400CN much too. And I always tweak them in "real" BW too, cause the Photolab is treating the BW like any other Colorfilm and is pulling it through its C41- Soup. The results are often a little colored, like the film is not really irrigated enough. Once I chose a really BW- Development at the same Lab, and the Film was developed correctly. No Postprocessing needed, but it cost me a lot of bucks. So I postprocess my Scans myself and save the money for the Lab and take the cheap C41.
So, don't worry