We are refurbishing a relatively small ground floor shop fully compartmented with the only other floor above. Main Street small town. Travel distance is slightly over 20m to the single exit. BC have turned our application down on the grounds that TD exceeds 18m. The guidance supporting our building regulations for fire safety in NI is Technical Booklet E. It allows travel distance to be extended to 27m in small premises but with the caveat that no floor area exceeds 90m2. ADB permits the same extension providing the floor area does not exceed 285m2. This shop has a floor area of 160m2. 
I am withdrawing the application and making a new one using ADB to support my claim that I am meeting functional requirements. I could use BS9999 2017 but for some reason neither BC or NIFRS are happy with its use on existing buildings. 
What an interesting mess fire safety is!
 

To be fair BS9999 was primarily for new building design as an alternative to ADB (& devolved equivalents) and there were too many people cherry picking the 'best bits' out without the premises complying to all aspects of the standard when using it on existing premises (I know the author and he confirms my interpretation) so I can understand their reticence.

However if you are doing a full strip to shell & redevelopment that's virtually the same as building then there is more chance of implementing BS9999 in full and thus it should really be accepted.