To most people Catalonia is probably famous mostly for Barcelona football club and the Gaudi architecture found in the city. The Scots however appreciate the nationalistic emotions engendered by years of oppression by a bullying centre. In the Spanish civil war this area suffered under General Franco's right wing army and since then the government in Madrid has not lessened the hold over the region. The supposed United Kingdom comprises Four sovereign nations Spain about a dozen. If Madrid and the corrupt government found there (are all governments corrupt today?) allows independence for Catalonia then the Basque region and others may decide also to secede from Madrid rule and that would upset many people.
While the thuggish police assault Catalonians attempting to vote peacefully many world leaders remain quiet. Theresa May and Jeremy Corbyn have said nothing as far as I can see, Boris Johnson mutters about 'constitution' and keeps quiet, only Nicola Sturgeon has spoken out against the violence and a demonstration against the violent crackdown occurs outside the Spanish consulate in Edinburgh with no riots.
The reason they keep quiet is the fear if Catalonia win independence others will follow Scotland certainly will and with Brexit bringing economic collapse sooner rather than later this is at least one good thing to come out of this corrupt and incompetent government.
The sad thing is that had Madrid allowed a referendum, indeed encouraged one with appropriate questions (to their advantage) a peaceful result may have shown no complete desire for independence. However now they have assaulted so many and revealed their desperation it is not unlikely that Catalonia may declare UDI and break away anyway. What could Madrid do about that? What would the result be? We wait and see.
The right wing media and the BBC are playing it down of course, they follow the Tory line.