These are plot theories and rumours from prior to Thatcher's rise to power and Thatcherite cultural revolution in the UK.
There was a TV series, two part one, which was called A Very British Coup which engaged with the idea of an internal coup against a popular labour government which would engage in some truly radical restructuring of the economy, social reform and changes to the "special relationship" with the US which dealt with similar themes.
There was/is a comic strip from the UK comic book 200AD which dealt with the idea of a radical being elected in the UK and changing the special relationship on a popular mandate too, this results in the invasion of the UK and seizure of its oil resources by a Russian dictatoship, The Volgans, named for the river Volga which was near the home of the Russian nationalist general who leads them.
The more recent strips are interesting because they depict atrocities such as kidnap and beheading being committed on UK soil and the obvious comparisons are with the oil wars and occupations in the middle east by the western powers but there's a pretty uncritical acceptance of the realpolitik idea that any UK government alienating the US would lead to the UK's desertion by the US and the EU being worse than useless at assisting if there were any hostile moves against the UK.
What I find interesting about it all is that I'm reading this in the wake of the whole Thatcher Funneral which a lot of people in the UK still find, like me, baffling, she was buried with serious state ostentation, despite alienating most of the political establishment and the royal family and having to be removed from office by their own party pretty much. It makes me wonder if the militaristic nature of it and military overtones mean something else, that Thatcher was the military and intelligence agencies candidate, it also makes me wonder about their power and intrusion on politics.