So I was just doing some basic sums. A little under 92% of Catalan voters who turned out yesterday voted in favour of independence. The overall turnout, suppressed by Spanish state violence, was 42.3%. This means that roughly 38% of the entire registered electorate voted Yes. You could therefore take the turnout all the way up to 75% (not all that far short of what was achieved in the free and semi-fair Scottish referendum), and still be guaranteed of a Yes victory even if all the extra voters were No voters, which would obviously be extremely unlikely. In reality, even a turnout in the low 80s would almost certainly have produced a Yes majority.
Spain now has a massive legitimacy problem. Even the dogs on the street know that Catalonia is being held captive within Spain by means of thuggery. All that Madrid and its apologists have left is the claim that the vote was not "free and fair" - but the problem is that (very unusually) it was the losing side that ensured it was not and could not be free and fair. The losing side also has the capacity to hold a free and fair re-run at any time it chooses. The onus is therefore on Madrid to either organise/facilitate that re-run, or accept yesterday's result. Doing neither is simply unsustainable in the modern world.
I hope the Catalan government's success in creating new facts on the ground by holding an unauthorised referendum has been noted by the SNP leadership. Thankfully, I doubt if we would have to face British state violence, but if London remains intransigent we might (at some point) have to be brave enough to get the ball rolling without a Section 30 order.
Incidentally, on the subject of London wanting a "strong and united Spain" (and to hell with the democratic choice made by the Catalan people) - I presume that means we'll be handing back Gibraltar? Madrid does, after all, regard Gibraltar as being every bit as much part of Spain's "indivisible territory" as Catalonia is. Exercises in Gibraltarian self-determination have been held in exactly the same contempt by Spain as yesterday's vote.