I put a couple of greyhounds in my Mini (I think it's still the same basic size as the current gen). It is certainly much larger than the original, but smaller than a Clubman so I have to wonder what your Yorkie looks like ;-)
I've only seen a Clubman in the street from the outside, and the estate bit looked like 20cm or so with the seats up. Obviously that's at the windows line so there's probably a bit more room lower down... So with seats up less than a Shepherd (or greyhound) shoulder width. Seats down, sure...