The ruling parties of Scotland, Wales and Northern Ireland published a joint statement in Cardiff on 14 September; timelines differ, but the direction is the same.

The Scottish National Party, Wales's dominant party Plaid Cymru and Northern Ireland's major coalition partner Sinn Féin gathered in Cardiff on 14 September and agreed that the political future of the three nations should be determined by their own peoples, not Westminster. Bianet reported the news.
With the devolution settlement that came into force in 1999, autonomous parliaments and governments were established in the three nations outside England; however, the final say on fundamental areas of sovereignty — spanning from defence to foreign policy — remained with Westminster in London. The three parties' joint statement amounts to a direct challenge to this equation.
At the centre of the debate is not the monarchy or the royal tie, but the question of where sovereignty is located. For Scotland and Wales, independence does not mean the severing of a symbolic link with the British Royal Family; it means the transfer of legal and financial powers currently held by Westminster to Edinburgh and Cardiff.
The path and timeline the three parties will follow diverge from one another; while independence referendum discussions continue in Scotland, Sinn Féin in Northern Ireland prefers to keep the reunification agenda alive. Yet the three parties converge on at least one point: Westminster must be prepared for possible constitutional change and cannot shape the process alone.
The three main parties of Scotland, Wales and Northern Ireland emphasized that they want to determine their own political destinies independently of Westminster. Although the three nations have had their own parliaments since 1999, they continue to remain under London's control on defence, foreign policy and fiscal matters.
A constitutional tension is growing in Britain: independence movements are not merely symbolic, but are fighting for legal authorities. This conflict will determine the next steps in elections and referendums in Scotland, Wales and Northern Ireland.