I have continued with the flower areas today but I'm a little frustrated with the contrast in colour. Paint can never replace light, but it is possible to create the effect that light has on colour. This is my struggle with this section of the composition. I cannot seem to create the light effect that I want. Using blue with the warm shades of magenta, seems to 'dull' the effect.
I shall not give up, but suspect that, when I need less blue, I will find creating a sun-lit sensation will be a little easier. The flowers in the right of the composition  are more pure magenta than the ones in deep shadow. The palette that I am using for the flowers is Rose Madder Genuine, Quinacridone Magenta, Ultramarine Violet, Cobalt blue and French Ultramarine, all from the W&N Artists' Water Colour range. I might experiment with other colours if I can find suitable ones in my supplies!