Thank you for your suggestions..

I am looking at crape myrtles at the moment and there are some
semi-dwarf varieties where the height is about right. Not sure on the
form though, but they are pretty when in flower.

I am still looking at options such as a weeping cherry (not sure on
height), hibiscus, plumbago etc. There is no restrictions such as
powerlines or depth issues (it is on the backyard side of the fence) so
if anyone has any other ideas I am more than open to suggestions. I am
looking to get them in the garden in the next month or so.