Of course I agree that we should always work to better ourselves, but I don't agree that we should be mixing up 2 different standards into 1.
By this I mean BS5839 and BS7671.
If a landlord is responsible for the maintenance of both the fire detection and alarm systems, and at the same property, the general electrical installation, then that landlord should be aware of the need to employ competent people who are skilled in both disciplines. And that such people should also have the full knowledge required, along with the correct forms of certification required for each type of system being inspected and tested.
Which may mean getting 2 different contractors in, ie a fire alarm engineer, and an electrician.
In some cases (though in my experience, not many), both tasks could be accomplished by the same contractor. But as I said before, there will be 2 different, distinct, forms of certification and/or reports, with very little crossover between the 2.
In my opinion....