How about Britain's Trees? I have a whole box full of them, but sadly haven't come around to painting them just yet. They're long out of production, so you need to scour Ebay and other sources, and not all tree types would be suitable, but the oaks are great.
I am not entirely sure about the height, but by my memory, they're about the height mark you specified.
I especially love the foliage, as it's perfectly scaled for use with 28mm miniatures; each individual leaf is cast, which (to me) is a lot better than clump foliage or flock. the only downside is that it's made of a bendy plastic, so it remains to be seen how well it will hold paint, but with some washes/inks, I think a good result can be achieved.
But if you're not fold of the foliage, the tree armature itself (which is modular btw; you can place/switch/rotate all major branches) is great too. It's suitably large to work as a 'real' tree in 28mm, while not being too overly large as to be impractical on the table...