Hardiness of Alyogyne heugelii

I have noticed my specimen of A. heugelii seems to be fairly hardy in Cornwall. So far it has been growing under the protection of a Cytisus and is being swamped by it.
Iwould like to move it to a slightly more open position so it can develope to its proper shape.
What temperature will it survive?

Sincerely,
Peter Jack

On plant Alyogyne huegelii