Onions and Garlic are ready for harvesting. Ideally after lifting the bulbs should be left to rest in the sun to dry but with the weather so variable thats a bit hit and miss. An alternative is to dry them in the greenhouse using the wooden slats to rest the bulbs on. This is ideal for both onions and garlic. It's better to clean the soil off the garlic bulbs when you first lift them because as they dry they can become more brittle. This can cause the head of garlic to break up as you try cleaning the soil off even when its dry. Although it seems counter intuitive, its better to clean the garlic when you first lift it as the bulb is firmer. Once dry both garlic and onions want a light place for storage, they will keep in an unlit conservatory for months.
The photos below show garlic as lifted, then ready to dry in the greenhouse which is exactly the same for garlic and onions. Garlic drying after being cleaned and finally hanging up in storage in a bright cool place.
For more about growing onions