Any advice on this plan for my front yard?

I live in northern Belgium. The left side of the garden gets sun from 1 PM until 6 PM or so. The right side gets just 1 or 2 hours of sun. My front yard is currently fully tiled. It's important for me to bring some life to that area.

There's currently a layer of sand of about 30 cms, below the tiles. Below that is sand cement. My plan is to break up the sand cement, see what's underneath (hopefully normal soil), take half of the sand away, mix the other half with soil from my back yard. Is that a good idea, or should I really not do this? (The back yard has 30 cms of soil mixed with gravel, then 70 cms of soil with lots of worms, then dense sand).

I have selected the bushes based on them being green in winter, and being relatively quick to grow. Two of the bushes are for some colour in winter and fall (ilex and pyracantha).

The spaces between the bushes are to provide the bushes room to grow. My idea was to put some filler plants there until the bushes grow big enough.

I'm not sure if I want to have the ilex aquifolium; I read that it's not a fast grower. I have no idea what to put in its place though.