All rented properties are legally obliged to have annual electric and gas inspections, as well as there being marked fire exits and fire alarms. Ideally he (the landlord) should have made these available to view before signature of the tenancy agreement(s). I would get your sone to aske to view these and if they are not available then he should immediately terminate his tenancy, hopefully he hasn't caused any "damage" other than ware or tear to the property, and uopn the landlord saying he doesn't have them (again, ideally) your son should inform the landlord that he is reporting him to his local council (the council upsholds the regulatory checks to rented properties) hopefully this will kick the naldlord up his bum and retuen the deposit and rectify the propert for future tenants