Quick tree decision needed!

The willow.

Hawthorn

Crab apple, so you can make jelly

if you want small, I'd go for crab apple, white or red flowers in spring and small colourful fruit in autumn. Birch will grow tall, blackthorn and hawthorn both pretty flowers but will form a dense shrub with thorns. Goat willow not particularly pretty.

Crab apple look really beautiful in the spring, and are easy to keep to shape. Nightmare in autumn when the little apples are falling all over your lawn and going mouldy (and your stupid dog is trying to eat them all). On the plus side you get lots of birds coming in to feed off the apples.
Silver birch are pretty, but not lots of leaves for coverage, and will grow taaaalllllll.
Blackthorn is more bush like, so lots of fence coverage, has thorns, so not great if you have small children maybe, but does mean you will have your own supply of sloes for making sloe gin.....

Crab apple for jelly.

Not the silver birch. You will not keep it at 6 foot.

I'd go for crab apple

Crab apple all the way. Pretty blossom, productive, usually have a lovely habit.

We have birches and they're massive

Can you grow a crab apple in a pot

@Crazycatstory has it exactly right.

upload.wikimedia.org/wikipedia/commons/c/c0/Common_hawthorn.jpg

Beautiful

Crab apple.

Silver birch. It grows tall, but doesn't spread outwards so much. And there's something ethereal about the rustling of the leaves. I've got one in my very small back garden.

Ok just re-read 😳 It will not meet your 6ft requirement!

Crab apple, beautiful flowers in spring, bright fruit in autumn. Able to keep to 6ft.