If you are providing a periodic inspection of the emergency lighting then you would need to define the deviations from the current standard on the report. This is not a case of pass or fail, it is a report on the installation at the moment. You cannot really refuse to issue the report because the installation does not meet the standards, that is the purpose of the report, to identify these issues.
If you have concerns then these can be raised in the report and then the landlord can decide on the action they wish to take.
If you are stating that the system does not comply with the current standards then you would have to classify the deviations in reference to the standards.
For a house as an HMO I would usually expect that the lighting you describe would be adequate, however if it is a very large building and the route from front to back is part of the escape route and has no borrowed light and there are changes in level and direction as well then additional lighting would be required.
It would be best to review the risk assessment for the property to ascertain why the system has been designed as it has, since this may clarify the reasoning behind the arrangement.