I have learned (well, yesterday) that:
1) I am an utter and thoroughgoing div. Well, not learned, just reinforced
2) The steel that bottom bearings are made from means that it is not practical, faced with a seized drive side bearing, to grind off the face and then hacksaw through to remove. Trying to do so leaves a conundrum that will need a chunk of metal welded on to the stub of the bearing, and has potentially trashed the frame. See item (1). I may try a diamond blade on a reciprocating saw, hacksaw just slides over.