Sacha wrote in :

A 'small tree is 15' - 26' tall so I think 12' is going to be hard to
attain. Have you looked at Eucalyptus which can be kept at the height
you want? Some of the flowering cherries would be beautiful, like
Prunus Shogetsu but that goes to around 16'

I started off considering a fruit tree - the kind that has been grafted to
dwarf rootstock to limit its height. I may end up going that route. I have
seen cherries with the sort of shape that would suit. I guess I can cut the
lower branches off to achieve a suitable shape if necessary.

On second thoughts, consider a tree fern, Dicksonia antarctica.

That's an interesting idea - thanks. I've never paid attention to these.
They remind me of something from the Mesozoic Era! That would be different,
certainly. Possibly a tad too different, but yes, certainly worth
considering.

Al