Kurnal
I think it is quite obvious that it is a guest house. As much as you want it to be a HMO to allow the window escapes I am sure that you know it is not a HMO.
PhilB hit the nail on the head. Basically use the risk assessment process as intended. You may have to be brave and take the fire service on though. (Or they will have to be brave and take you on, depending on which way you look at it) Remember your/their defence is to be able to prove "It was not reasonably practicable to do anything more"
twSutton, I think that section is pointing towards full time students and wherever they may live, not a particular type of premises. So wherever they live, if they are away from what they may class as their home (i.e. Parents house) but living in digs, they are occupying that premises regardless of it being a HMO, student flats or house etc.