You can find a list of known and probable cabin allocations by clicking on This Hotlink Cabin B-1 does exist, but if it was occupied, the name of the occupant has been lost to history.
As far as I know, B deck accomadation was entirely 1st Class as far as the actual cabins went. The only 2cnd Class facilities there were the 2cnd Class Smoke Room as well as the enterances.