According to airbus : if no flare at 30ft
If visual reference are sufficient
Disengage the autopilot and complete manually the landing
Nevertheless some operators SOPs order a go around in case of "no flare"
The key is in the interpretation.
To me, "if visual reference are sufficient" means that the vis is not really a CAT III vis, because if it is, visual cues will not be sufficient.
Conclusion, in actual CAT III vis, if there is no FLARE, don't hesitate, don't assess, just go around.
If actual vis is CAT II, the has captain
already been seeing the visual cues well before the time you reach 40 ft, he will disconnect and land if you call "NO FLARE".
So there is really no decision as such. It is a direct thing. You should know well
before the FLARE mode activation height if you have sufficient cues or not. If you don't, a GA will be necessary if there is no FLARE mode.
In the 320 alert height is 100 ft, which is the same as the minimum CAT II DH. It has been stablished that any lower than that you will not have enough visual references the sufficient time to make a landing.
Therefore I consider that as the last chance to condiser myself able to visually land. If by the AH I don't see enough lights to be able to land, from then on there are only two options for me: autoland or go around.