Thanks for your reply, Tee Gee. I will have to put it in a polystyrene box in the greenhouse and put fleece over it as the gh is unheated.
By giving it that treatment, I managed to keep a Gerber plant safe throughout the last winter. I took the fleece off on warm days and gave the plant some water. When it was time to put it outside, it was covered in buds and then gave a beautiful display.