Apologies if I've said this before but it's worth repeating exactly what happened in Crimea:
The parliament building was occupied by armed men, who stood guard menacingly while a selected group of deputies was admitted, to vote for and to swear in a new government and PM - the new PM incidentally, Sergey Aksonov, being a member of a minority party in Crimea and a former mobster (although admittedly he's not the only mobster-politician in that part of Ukraine, a fact that is very important in understanding that country and also Russia).
Aksonov then, almost certainly as planned by his "mafia bosses" in the Kremlin, asked Russia for help "protecting" the ethnic Russians there, despite not even the heavily propagandistic Russian media being able to dredge up a single, solitary instance of any threat to them. A "referendum" was called and twice brought forward. Cameron says this was done at the barrel of a kalashnikov, and he is right: it was, effectively. Ukrainian TV channels were taken off air, Russian naval forces not only from Sevastopol but bases from the Russian mainland, then moved in and started systematically taking over or surrounding key installations. People were intimidated, some Tatars had white crosses painted on their doors in acts reminiscent of the Stalin years.
In fact, about 60% of Crimea roughly is ethnic Russian, and by no means all of them historically supported a reunion with Moscow, so in normal conditions a referendum, even were it legal and constitutional, would have been much closer.
No proper voting figures for the referendum have beeen released. In so far as one can talk about an "electoral register" then some indications suggest as many as 123% of the entire population of Sevastopol may have voted(!)
In short, not democracy in action at all, but flagrant international piracy. Comparions with Kosovo, unsatisfactory as that may have been, are ludicrous.