Shrubs for heavy clay
 

Hi all. I've joined this forum to see if anyone has any good ideas for my current garden problem! We've recently had a 5 bar sliding gate fitted which slides behind a 5 bar wooden fence. I had originally intended to plant some small shrubs in front of the fence such as maybe a berberis, hebe or similar. Trouble is, the soil is actually extrmemely poor and is very heavy orange clay. Is it worth me spending a while trying to dig away some of the clay and replacing with topsoil to plant something or will nothing ever grow? I didn't really want hawthorn as we have this around the rest of the boundary and I was hoping for something a little different.
Does anyone have any suggestions for some evergreen and/or colourful, shallow rooted shrubs about knee height that will tolerate this kind of soil?
Many thanks!