Some nice pictures of the flowers and some advice on the best type for your garden on these sites. Crab apple fruits are so pretty, like Christmas tree decorations all winter.
All crab apples do flower, and set with nice coloured fruit too. Different varieties have different coloured fruit. They also attract the birds to the garden in winter.
I love crab apples - the blossom seems to last for much longer than regular apple trees and doesn't blow away at the first gust of wind. For this reason they act as excellent cross pollinators for almost all eating apple trees if you wanted to include a regular apple tree in your garden.
The crab apple fruit itself - whilst unpleasant to eat raw - does make excellent crab apple jelly.
In terms of which crab apple to choose - my experience is:
John Downie - pretty and large fruits but very susceptible to disfiguring scab and the birds usually finish the fruit by October.
Everest - usually smothered in fruit - orangey colour. Birds and squirrels usually finish the fruits early to mid winter.
Red Sentinel - beautiful bright red fruit - the birds don't usually finish this one off until late winter.
There are lots of others but these are the ones I have.
You could also consider a hazel / cob nut tree if you like nuts and want your garden to be productive. Mine are probably 15 - 20 years old and are about 4m high. A denser canopy - but it can be coppiced if it starts to cast too much shade.
BTW - I'm also on clay soil so these should be ok for you.
Another lovely crab apple is Malus Golden Hornet - beautiful pink and white blossom in sprint and long lasting golden fruit decorating the branches all winter, a bit like golden balls on a Christmas tree
attractive to birds and fabulous for crab apple jelly
I have an annoying privacy issue due to neighbours behind having large windows on the side of their house that look directly into my garden.
I've mixed laurel and photinia red robin in with flowering cherry trees and also a sorbus (whitebeam) which allows for evergreen privacy in parts of my garden but lovely flowers and leaves during the spring and summer. I have a prunus kanzan tree which I think is the beautiful pink one you posted above!
I'm not an experienced or skilled gardener as only been gardening a few years but think it works well and I'm slowly achieving a better and more interesting screen each year!