It is clear that building regulations are not being met and since building regulations have the purpose of providing for the safety of persons in and around buildings, the conclusion might be that the arrangement is unsafe. My original question was about quantifying the risk. Slapping another load of concrete down may, on the face of it, seem to be a mitigating measure, however unless accompanied by a landing area, kerbs guards etc it still remains unsatisfactory as far as building regulations are concerned. So, in order to reduce risk you must first of all establish the level of current risk. Fire risk assessors advising on mitigating risk may do so with good intention but if the remedial work necessary still remains non-compliant, perhaps even introducing other unintended risks, then the assessor could find themselves subject to a negligence claim.
Hardly a no-brainer!