Joined: Jan 2010
Posts: 9,835
Likes: 1,816
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Sounds like the OP's bb assembly simply pulled apart on the wrong end when it was removed.
I would set the vice jaws to the major diameter of the body of the UN72, with the stuck left-side cup resting on top of the vice jaws.
I would then blast the threaded left-side cup threads with a propane torch for 15 seconds, then tap the end of the spindle so the bb body moves down through the jaws with the cup left sitting on top of the vice jaws.
Hopefully this gets the cup free of the body with only minimal force applied to the end of the spindle.