[Goosegirl]

My niece would like a small ornamental cherry tree mainly for its blossom so has anyone got any recommendations?

[Beloved Porcupine]

There are lots out there, so I can only comment on what Is in my garden 

I have a Kojo no mai,  a nice pot specimen which grows slowly.  It will eventually reach 2 meters in 20 years (but can be pruned).  Dainty white flowers.  Nice to put on the patio or by a window in the spring.  We bought ours about 4 years ago and still only a couple of feet high

In the ground I have a Kiku-shidare-zakura (aka Cheals Weeping cherry).  This is a nice small tree where the branches grow down to the ground.  It is supposed to reach 2.5 -4 meters in 20 years (a bit of a large range, eh?).  Lovely pink blossom.

There many pics of these varieties online.  Good luck!