I'd like a little more info on how the "Dictatorship" in the 80's came about.
What happened to the Queen for example?
The dictatorships origins actually arose on the early nineteen seventies. The basic POD is that the hard left causes more trouble for Hetah, but also alienates the centre of the Labour Party, which collapses into two factions (The Labour Party and Social Democratic Party (Later the reunited LSDC) ).
Heath meanwhile becomes more centrist and corporatist as politics become more radical and alienated. This puts off many of the more right wing members of the Tory Party who, after Margaret Thatcher leaves, break off to form the National Democrats. After the nineteen seventy four election there is a narrow Cinservative Minroity propped up by coalition with the Liberals. The perceived shift to the left by Heath sends more conservative voters to the Nationals under Thatcher.
Role around the nineteen seventies and the Hard Left and Hard Right are fighting on the streets, largely United under the two radical new parties (although the Hard Left is technically still the Labour Party). The Conservatives and Liberals form the CLA and run in the election as basically one party. The result is a strange one, and the Nationals get a majority of votes (based on a message of strong foreign policy, a crack down on the strikers that plague the Heath governments final years, and monetarism saving the economy) but the CLA and Social Democratic Party (The centre of the former Labour Party) form a coalition to keep them out.
The hard left is still displeased, and a General Strike is called. Three months after the general election a bomb explodes in an empty House of Commons chamber, destroying much of the palace. This is revealed years later to have been the work of the National Front. Seeing the country in turmoil and a mandate from the public Thatcher enlists the help of Mountbatten and the army to overthrow Heath's National Government and installs a Thatcher led National administrated military backed Junta in power. The queen tentatively supports this dictatorship.
The dictatorship is basically an even further right Thatcher government, and lasts a similar length. They privatise almost everything (with the NHS a major exception) and impose ridiculously tight immigration restrictions. Britain leaves the EEC, but only before it can be kicked out. Defence spending is increased and a police crackdown on dissent is made.
The dictatorship falls as the "Warsaw Spring" sweeps Europe during the (much bloodier) collapse of the USSR. Inspired by anti-communists in Eastern Europe, many Britons rise up and try to overthrow the dictatorship. Thatcher realises her days are numbered, and re-establishes Parliament (in a new building across from the Palace of Wrstminster) and requests the Queen dissolve her government.
The dictatorship is, after eleven years, over. Democratic elections are held later that year, and the LSDC wins a five year term. They win the next term in 1995, but lose to the CLA in 2005. Gordon Brown wins it back for Labour in 2010 and, in a controversial move, removes the ban Labour originally placed on the Nationals from re-organising as a party. And then in 2015 we get the mess shown in the vignette.