this one isn't hardy - you say its in West Sussex, which might mean its not that far from the sea, where it'll be much milder in winter. That, together with the mildness of last winter, and its sheltered position behind a wall, might explain why, if it did survive outside last year, it has done so.

If you want a hardy one, it'll have to be Zantedeschia aethiopica 'Crowborough', which has creamy white spathes.

Thank you very much I will go for the hardy plant.

You could always have skunk cabbage which is yellow and hardy.