I'm not sure what bella Italiano garlic is, other than just the name of a particular variety of garlic. As with all garlics you should leave them until the leaves turn yellow and start to die back, as this is when the bulbs will have reached their largest.
That is the time to harvest them and dry them out. Here in France that's usually around late June or early July but it depends what part of Britain you are in for when yours will be ready.