I'm curious myself. Deciduous plants often sprout and bloom at the bottom, first, but I'm not even seeing dormant flower buds on the upper branches, in this case.

Very odd, is the top half of the tree in windier conditions by any chance?

There is a wind corridor between the corner of my house and the laurel hedge but not sure whether that would affect the magnolia considering its location? It's about 4-5 metres away. Strange.....

I'd give it few days - there's certainly visible flower buds on most of it, but hard to be sure if there's any in the top quarter at this stage.

Thank you very much for posting photos with you question. It helps a great deal. I see a sunny day, yet your stellata is languishing in rather dense shade. I don't think it gets enough sun. This is the end result. It wants to bloom. It's struggling to bloom, but it's missing the key element - sun. Even dappled sun would be an improvement. In nature, they are an understory tree, that blooms before the maples and oaks leaf out so the sun reaches them.

Anyway, I thought you would like to read these responses on magnolias from another site. Scroll down to read the comments. Interesting?

http://forums2.gardenweb.com/discussions/1633402/transplanting-magnolia-tree

There seems to me to be a lot of buds however it is not unusual if your plant made a late spurt of growth late last year the ends would not be mature enough to support flower buds.
i would have thought it unlikely that you did not have sun there in some part of the day