Re-watching K-On! I would say Tsumugi's crush on Sawako-chan is actually the most yuri part of the show, followed by Yui's for Azusa. Which makes it interesting people think Ritsu/Mio is the big couple. I guess they're the most reciprocal pair. I think Yamanaka-sensei's problem with men, even though she's beautiful and popular, is a problem Mugi can fix.
Mio and Ritsu are pretty much a married couple, just remember their class play in the second season.
But I got to admit that I re-watched K-on after whatching love love sunshine and was surprised how little Yuri K-on has in comparison.
Still love K-on the most thought.