Q.Choosing the right plants
I have just made a garden 18m x 1 1/2m running E to W with a 2m paling fence along the N side. I am not far from the beach but the soil is mainly clay. The problem is that in the winter it will be mostly shaded by the fence but in the summer, it will be very sunny and hot! We live on the Sunshine Coast , Qld. Initially, calistemons did well here…..which I would be happy to plant again, but what could I plant in front of them, that would flower often and be able to cope with the conditions?

Amending your clay soil will help with drainage and allow you to choose more plant types for your zone.
These links will help you.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-to-improve-clay-soil.htm
https://www.gardeningknowhow.com/special/xeriscape/drought-tolerant-ground-covers.htm
https://www.gardeningknowhow.com/special/xeriscape/drought-tolerant-flowers.htm
https://www.gardeningknowhow.com/special/xeriscape/drought-tolerant-perennials.htm
https://www.gardeningknowhow.com/special/xeriscape/xeriscape-landscape-design-ideas-for-clay-soil.htm