Where does the visiting contractors bit come from? It is not a place of employment unless there is some form of construction going on. The CDM applies.
Contractors might be employed to come into my HMO to maintain the emergency lighting for instance.
CDM regs therefore don't apply!!!
The contractors I employ should expect to be able to work in a safe environment, so as a landlord of a HMO I have a duty to make provision for the safety of anyone whom could enter or use my premises.
If we dont provide extinguishers for residents I might ask the contractors to bring their own FFFE provision (infact this might be compulsory if they are doing hot works), or failing that I'd induct them to evacuate only, and not attempt to fight fire as there are no fire extinguishers present.
If a resident wants to provide his own extinguisher then thats his perogative and therefoere his own responsibility not the landlord's.
Nobody here has suggested extinguishers are there to protect the means of escape, and visiting contractors wouldn't necessarily be confined to building sites.