An uproar- just as is happening over Hilary Mantell's Thatcher assassination story? Yes, exactly like that.
Actually, I'm trying to imagine it and failing. No figure on the Left is as divisive and iconic as Thatcher was and continues to be. She has an era and a political philosophy named after her. Foot and Benn have neither. Foot was a place-holder leader of the opposition, Benn a political misfit who morphed into a national treasure. Foot is almost forgotten, Benn will be forgotten in a decade. They are historical footnotes- and it's hard to imagine anyone shooting them or writing about shooting them or kicking up a stink about a story in which they get shot. The only Labour figure who matters as much as Thatcher is Tony Blair- and the Left hate him as much as- if not more than- the Right.
Also the Left doesn't have a rag like the Mail at its disposal to confect outrage on its behalf.
I've read the story. It's not implausible. A middle-class woman, a little like Mantell, has her flat taken over by an IRA sniper with designs on Thatcher- and choses to assist him. It's both a thought experiment and a valid fictional reflection on a particular time. Yes, people hated Thatcher enough to want to kill her. That's an historical fact. Glover and his lot seem to want to rewrite the record and have Thatcher's memory be nothing but flowers and fruit.