> In 2014 there was no talk of the UK leaving the EU.
My memory is that the chances of the UK leaving the EU were used by the SNP in 2014 as a reason to vote for independence. The Scots independence vote took place on 18 September 2014. Here are some key events that took place leading up to that ...
https://www.bbc.co.uk/news/uk-politics-15390884
22 January 2013: In a long awaited speech Prime Minister David Cameron says that if the Conservatives win the next election they would seek to renegotiate the UK's relationship with the EU and then give the British people the "simple choice" in 2017 between staying in the EU under those terms or leaving the EU. His speech comes against a background of polls suggesting UK Independence Party support at 10%.
5 July 2013: The Conservative backbencher James Wharton brings forward a bill to enshrine in law his party's pledge to hold an in/out referendum in 2017. It passes its second reading by 304 votes to 0. It goes on to clear all its Commons hurdles before falling in the House of Lords.
31 January 2014: David Cameron says the Conservatives will bring back the Private Member's Bill and said he was prepared to use the Parliament Act to force it into law, rather than seeing the Lords block it again.
5 March 2014: It is announced that the BBC is to host a TV debate on Britain's future in Europe between UK Independence Party leader Nigel Farage - whose party is riding high in polls ahead of May's European election and who wants an immediate in/out referendum - and Nick Clegg, whose Lib Dems say they are the only "party of in" when it comes to the EU.
12 March 2014: Ed Miliband writes an article for the Financial Times in which he says that Labour will not hold a referendum on the UK's membership of the European Union unless there are proposals to transfer further powers from London to Brussels.