My first attempts in early spring, at just cutting in half and suspending in jars of water using toothpicks rotted off. I then tried in bags of compost, again just rotted off. Then I read that the tubers sold in shops are treated with an inhibitor to stop them sprouting. So I then gave them a good scrub, and again suspended in jars of water and this time they sprouted. I'm not sure if its the scrubbing or the exceptional weather but one half at least has put out a lot of growth. I have now put them into pots of compost.
I think I will attempt to seperate the shoots from the tubers and overwinter as house plants.