First, agapanthus are not lilies, despite the common name of lily of the Nile. They are fleshy rooted herbaceous perennials. The easiest way to overwinter agapanthus in areas where it is not hardy is to grow in containers and store in a protected area over winter (cool basement, garage). They should go dormant in winter and so not require much light and only enough water to keep the soil barely moist.

Thanks I'll try that.