I see from the dustbin that you're in Staffordshire, UK. Are you planting these in the whole L-shaped bed? There don't seem to be a lot of plants for the whole thing, but you could plant the ones on the blue dustbin in groups at about 9" inch spacing within the group if you're growing them as annuals, although they may be perennial in your climate. I know the silver one is perennial there (used to be called Senecio cineraria but that might have changed - I don't recall the common name in the UK being dusty miller like it is in North America). If you're planting it as a perennial the spacing should be wider. Does the pink-flowered individual plant have a label? It does look like a hibiscus/mallow/lavatera....