I think it is important to remember that many B&B's are still domestic dwellings.
Before I moved from FP, there was a great deal of discussion in the office on this and a common standard was agreed, which was a grade D LD2 system with heat detection in the kitchen.
Fire doors were not deemed necessary but doors were to be in good repair and well fitting.
Discussion with the owners often reveals how much of the time the B&B is used, some are full time and some are during holiday season to make a few more pounds, so this had to be considered. We were aware that demanding a full alarm system and fire doors etc would not be reasonable nor practicable in many cases.
We have to remember that the fire safety provisions should be apropriate to the risk ... early detection and warning was considered the most important to protect life.