Here is a quick rundown on some of Europe separatist movements:
Population of proposed region vs population of country as a whole: 5.3 million vs 63.7m
Year independence movement began: The Scots National League, inspired by Ireland's Sinn Fein, campaigned from 1921, 214 years after the Treaty of Union ended nearly nine centuries of separate statehood.
Support for referendum: A poll for The Scotsman newspaper in March found 41 per cent in favour of independence, 46 per cent against, although the "Yes" support was the largest recorded in the run-up to September's referendum.
Land mass of proposed region: 78,772 square kilometres
Regional GDP vs country as whole: $24 billion vs $2.38 trillion
Main separatist group: Scottish Nationalist Party (SNP)
Militancy: No recent history of violence. The SNP, evolved from the Scots National League, chose a constitutional path, securing representation in the UK parliament from 1967 and arguing that Scotland should have rights to North Sea oil revenues. First devolved parliament, controlling most domestic issues, elected in 1999.
Population of proposed region vs population of country as a whole: 1.84m vs 6.4m (whole of Ireland)
Year independence movement began: 1921, from the creation of Northern Ireland with the partition of the island.
Support for referendum: Sinn Fein which wants a fully independent all-Ireland state, is the second biggest party in Northern Ireland, where it shares power with politicians wishing to remain within the UK, and fourth biggest in the Irish Republic. A 2012 opinion poll found 18 per cent in Northern Ireland favoured an independent united Ireland. Support is greater in the Irish Republic (57 per cent in a 2010 poll)
Land mass of region: 13,843 sq km
Regional GDP vs country as whole: €37.33bn vs $2.38 trillion (UK) / $226.84bn (Irish Republic)
Main separatist group: Real IRA and 32 County Sovereignty Movement, offshoots of the Provisional Irish Republican Army (PIRA)
Militancy: Irish nationalists have fought for freedom from British rule for centuries. They reject the island's 1921 partition. Despite the peace process that ended the most recent 30-year period of conflict in the 1990s, dissident republicans continue, on a small scale, to use violence in pursuit of their aims.
Population of proposed region vs population of country as a whole: 7.56m vs 46.7m
Year independence movement began: First stirrings date from the 17th century but political parties began campaigning for independence in the early 20th century.
Support for referendum: Catalonia's devolved parliament plans referendum on the issue in 2014, in defiance of Spanish government objections
Land mass of proposed region: 32,114 sq km
Regional GDP vs country as whole: $255bn vs $1.39 trillion
Main separatist group: The Republican Left of Catalonia and the Popular Unity Candidacy (CUP) openly campaign for independence but the ruling Convergence and Union (CIU) coalition is seen as moderate nationalist.
Militancy: No recent record of violent struggle. All the main political groups support a referendum. Despite Catalonia's status as an autonomous community, The Spanish constitutional court has ruled that its designation as a "nation" is a historical term without legal weight.
Population of proposed region vs population of country as a whole: 2.16m vs 46.7m
Year independence movement began: First assassinations in 1968, nine years after creation of Eta.
Support for referendum: The separatist party Euskal Herria Bildu won a quarter of the vote in 2012 elections, while the biggest proportion of votes — one third - went to the Basque Nationalist Party, which seeks an undefined form of independence
Land mass of proposed region: 7,234 sq km
Regional GDP vs country as whole: $91.49bn vs $1.39 trillion
Main separatist group: Eta
Militancy: Eta has been blamed for 829 killings from 1968 to 2011. Several hundred activists are held in jail, mainly in Spain and France.
Population of proposed region vs population of country as a whole: At least 14m (much higher according to Kurdish nationalists) vs 81.62m
Year independence movement began: Demands for a Kurdish state date from late 19th century; armed insurrection began 1984.
Support for referendum: 59 per cent of self-identified Turkish Kurds said in a 2009 poll they did not think Kurds wanted independence.
Land mass of proposed region: 190,000 sq km
Regional GDP vs country as whole: N/A
Main separatist group: Kurdistan Workers Party (PKK)
Militancy: Armed struggle ran from 1984 to 2013 with the aim of creating a breakaway Marxist — Leninist state. Casualty figures vary widely but could be as high as 45,000 deaths (rebels, Turkish military and civilians combined). The jailed PKK leader, Abdullah Ocalan, now advocates a political solution.
Population of proposed region vs population of country as a whole: 2.4m (including Sevatapol) vs 44.57m
Year independence movement began: 2014 in response to Ukraine rebellion that drove the president, Viktor Yanukovich, from power
Support for referendum: A March referendum reportedly showed 96 per cent of the 81 per cent who voted favoured independence from Ukraine and federal status with Russia
Land mass of proposed region: 26,100 sq km
Regional GDP vs country as whole: $4.3bn (Autonomous Republic of Crimea) vs $175.5bn
Main separatist group: The Yanukovich-led Party of Regions was the biggest vote-winner in 2010 Crimean parliamentary elections
Militancy: While Crimea's vote to join Russia was largely peaceful, at least five people have been killed since pro-Russian militias seized areas of the peninsula.
* Colin Randall