Well fastest growing is a bit of a statistical anomaly, surely when coming from such a low user base, growth looks high. "the past three months to January 2014, show Android almost snatching 70 percent market share across Europe." so any fastest growth is still going to be way down on overall market share.
I also worry about stats like this when it is from an interested party 'Windows Phone Central.'
Interestingly there isn't a split in the collective stats for version number of the varying OSes.