The smallest cherry I know of is Prunus Ko-jo mai (or something like that anyway) - not sure if it grows as tall as 6 ft, but probably reaches 5 ft eventually. White blossom now!

Yes, exactly Shelia Kojo-no-mai. It does get to about 5-6' eventually but it's not a quick grower. Lovely though, really well worth growing. Lovely autumn colour and twisted twiggy growth....really nice plant, and one of the earliest cherries to flower.

Several more too. You can even get a larger flowered type called appropriately enough 'Little Pink Perfection' that gets to about 6ft.

That one sounds lovely!