Considering the time to turn out (response time) in addition to any delay in confirming the fire and contacting the fire & rescue service as described (total time to response). I would consider calculating worse case time to flashover and if possible within estimated total time to attendance, would then look at capex for sprinkler protection. Of course this would also depend on premises, stock and business interuption value. Agree that policy of not using PFE is a nonsense though.