I had one stuck this year, an original on a 1973 bike. Took it to a frame shop (Franklin Frames, near Newark, OH, Jack Trumble) and he had to spot weld a little piece onto it, then take it off neatly with any wrench. Not reusable, of course, but no damage to the frame.
Now, no offense to anyone, but this fixed cup removed clockwise. Maybe they all do, but i thought I'd through that in there. English frame.
Tom Joswick
Columbus OH