DozyWannabe,
The stall warning system looks at three values of AoA from three independent sensors. It sounds a warning if the highest of the valid AoA values exceeds the threshold defined by the highest of the valid airspeeds. If I understand correctly, the system can loose any two of those values and it will still operate on the single remaining one. In other words, the system is strongly biased towards giving a warning when required, at the detriment of unwanted operation. Yet, when all three AoA values suddenly disappear, the last valid value being 41.5 degrees, the system just goes silent. No warning, not even a message on the ECAM.