Just another thought to chuck in the pot: how about a weeping pear?

The fruits are ornamental only (and in fact I didn't spot any on our tree last year!) The flowers are out now, but the bees in our garden seem much more interested in the pulmonaria under it (and anyway the blossom doesn't last very long).

It is possibly more dense than you want, and I think it would naturally have a lower canopy than you want (I've seen pictures with branches nearly down to the ground). So you'd need to remove lower branches to sit under it: but the one in my garden is very small/neat and you can stand up under it (just), so worth thinking about. I think the leaves are beautiful, and all the photos I've seen suggest they naturally make a really nice neat shaped tree and don't seem to get too big. The RHS site suggests they are not too fussy about setting:

RHS Plant Selector Pyrus salicifolia 'Pendula' AGM / RHS Gardening

Let us know what you go with!