Its not a great design is it. One of the most common cause of fire is cooking and if in the bedroom you have to more or less circle the kichen area to reach the exit from the living area and then pass though another room containing a utility area. Personally I am not a fan of the inner room sprinkler trade off but as you say it is permitted in that flawed document BS9991.
I dont usually have much sympathy with the BCOs in these situations but to be fair its the applicants job to convince the BCO that the design is equally as safe as a code compliant design.
I think the 19m vs 16m is a red herring - its being used as a screen, the positive variation from the standard he can nail you with - the issue is the position of the kitchen and the additional room at the main entrance.
Sorry not to be more positive, its frustrating when you know there are many far more unsatisfactory buildings out there- but they arent applying for regularisation......