Do you have pockets of soil in the wall or can you create such? The plants wont grow unless you can do so and will need watering whilst they establish.

No plants will do very well without water,especially against a south facing wall..it will be in a rain shadow as well,so might not reach the roots where it is needed..you didn't say whether you wanted plants against it,or in it,as Mg has mentioned...

Aubretia will grow well in dry situations and not so good soil - I have several growing under a hedge but hanging over a north facing wall. My neighbour has spectacular aubretias growing in the same situation although hers is south facing and nothing is ever done to them. Lewisia is also good for dry soil as they hate their roots being too wet. Some forms of campanula grow in completely soilless places. I am going to post a picture of one.

sedums / stonecrops will manage as well.

I also have a south facing dry stone wall and lewisias grow very successfully in mine with very little attention, and they look super :-)

Hi everyone. Many thanks for your advice/help. I will now get this underway. To, Moon grow. They are intended to go in the wall. Yes there are places in the wall with space to insert soil, some larger than others. With a depth to the back of the holes around 4inch.

Many thanks to everyone for there help/advice. I will now get this project underway. Moon growe, yes I can put soil into some of the larger pockets with a depth of around 4inch to the back.

Then sedums, sepervivums, saxifrages, drabas, very small campanulas plus lots of others will work - but they will need watering in to start with... Love to see a photo in a year's time!