Leave them to die down naturally, but dead head them first. You can cut them off after six weeks, untidy, but they need this to feed bulbs for next year.

Personally Bulbaholic and I let the leaves die back completely. We also water once a week with half strength liquid tomato feed. Deadheading isn't really necessary but tidies the plant up a bit.

I've deadheaded mine and have now left the leaves to die back. I started feeding them last week ...in way Moon grower described some weeks ago...and will leave the leaves to die back. I hate the messiness of them though....do I really need to leave them till they are completely dead?

Izzy we let ours die back completely, yes it is untidy but that is part of the nature of a garden. Nature herself isn't tidy. If you get really desperate you can cut them off after 6 weeks but it will mean less food going back into the bulb for next year.