To preserve the breeze block, I would put a sealer everywhere the soil is going to touch, and allow it to dry thoroughly (several days) before filling the beds with soil. Planting a hedge in raised bed, remember that the bed will need to be at least as wide--from the wall to the inside front edge--as 1/2 the planned height of the hedge--from the soil level in the bed. Better also check council rules on hedge heights above walls.

Agree with Tugbrethil's comments - make the width of the beds a minimum of 3 feet from front to back. I have a query though - is your yard already completely paved, or is there soil there. In other words, are you building these raised beds on a hard surface like paving or concrete, or will there be soil beneath? Should be built on open ground, so that the plants have decent drainage and more root room, not over paving.

Have you thought of using climbers rather than shrubs, as they need less width. You could use roses or how about loganberries or blackberries?

Thanks for the advice everyone. There is concrete down at present but I will be taking that up, I also like the idea of maybe using the climbers along one side of the wall, especially Blackberries. If you have any other burglar deterrent climber plants please let me know I appreciate any ideas.

Pyracantha's a good one - not a climber as such, but likes to grow against a wall, wicked thorns on it, but will need regular pruning to keep it against the wall.