What to plant in an exposed boarder.

[Pipbin]

Here is my lovely garden in pictures taken when we first moved in. It is south facing but, as you can see, it has lots of trees and backed onto a park with even more trees.
The garden is terraced as its on quite a slope. We have taken out the lavender bush that you can see in the 3rd picture.
What could we put in its place?
We have been in our house for a year now, what other suggestions would you have for it?

I forgot to mention that the drop on the other side of the boarder is about 5ft. Not that it makes a difference really, but it does make it a little exposed.

That is not exposed, that is sheltered.

What I would put there is...some sort of black elder.

I guess it's not exposed really is it. I was just thinking of the drop on the other side and that it's not against a wall or fence.
I came from a terrace with a tiny courtyard garden.