I came across Thatcher's infamous The Lady's Not For Turning speech at the Tory Party Conference in 1980. She starts and ends her speech with references to the Labour Party Conference that had previously taken place in Blackpool:
This week at Brighton we have heard a good deal about last week at Blackpool. I will have a little more to say about that strange assembly later, but for the moment I want to say just this. Because of what happened at that conference, there has been, behind all our deliberations this week, a heightened awareness that now, more than ever, our Conservative government must succeed. We just must, because now there is even more at stake than some had realised...
I have always known that that task was vital. Since last week it has become even more vital than ever. We close our conference in the aftermath of that sinister utopia unveiled at Blackpool. Let Labour's Orwellian nightmare of the left be the spur for us to dedicate, with a new urgency, our every ounce of energy and moral strength to rebuild the fortunes of this free nation.
I've been unable to find any more detail on this, and the Wikipedia page doesn't note anything of interest. What exactly was this terrible spectre that Thatcher was referring to?