How about a crab apple on a dwarfing stock? You can find how big various rootstocks grow on line, and then hunt for a supplier.

Thanks steragram - nice idea. Also wondered about a Rowan.

Yes rowen would be a lovely choice, lovely foliage, berries and autumn leaf colour, a small multi stemmed Himalayan birch would look nice, or one of the cotoneaster cornubias that look fantastic when laden with all those red berries.

I always thought Cornus Kousa Dogwood was an attractive choice. It doesn't get too big - year round interest. Good performer in the garden.

Amelanchier canadensis would be a good choice. Flowers in Spring, berries in summer and lovely autumn foliage.

Yes to Amelanchier, or maybe Cercidyphyllum japonica (Katsura tree) which is slim, upright and doesn’t take up much space . . . very attractive small tree.

Hawthorn or Rowan for wildlife.

Rowan. You may be lucky enough to get waxwings coming forhe berries!

I'd also go for Rowan but chose a red or orange berried one. The birds don't seem to take the white and pink berries so readily.
I also have Amelanchier and Hawthorn and the birds really enjoy those berries too. There are some Cotoneasters that form trees rather than shrubs so that's worth looking out for.

You now need an extension because how are you going to choose from ll these lovelies?