Did the BA 146 not do autopilot CAT 2 manual land? The B732 certainly did. In triple auotpilot (fail operational), depending on company SOP's, you could go CAT 3 - CAT 2 (land 3 - Land 2) due to an annunciator change. If it became worse and 'no autoland came up then it was a manula CAT 1 reversion. In my outfit if owt goes wrong on a CAT2/3 it's G/A. (fail passive). Don't know why we don't revert to CAT 1, but it's their trainset.
So I suppose if a reversion Cat3-Cat2 is possible you need to brief that minima, and also Cat 1. But what else about the approach or G/A could be different?