When the leaves die back, lift underneath with a fork, leave to dry off on top of the ground. To pickle, take the outer skin off each bulb plus roots and top. Scald with boiling water, drain off when cool. Put in jars, fill with malt vinegar add a pinch of mixed spices to each jar, screw on lids tight, store in a cool place. They should be ready to eat in three months time.

thanks for the advice. looks like my onions arent ready just yet then. they looked the right size but the leaves are still a very healthy green

Lift them up, almost out of the ground and let the leaves dry back. You can bend the tops to help this process.