What stage to 'prick out' onion and leek seedlings?

[Sparkly]

My onion and leek seedlings have germinated and are about 1 inch tall. They are in seed compost. What is the right time to prick them out? I am going to plant them in toilet roll tubes. Is multi-purpose compost fine for this, or should I add anything? Also, once I have pricked them out can they go straight outside under cover?

thanks!

[Sparkly]

[growmore]

Your onions need prickng out into individual pots at the crook stage .(resemble a sheperds crook) this is usually 2 to 3  weeks or so after germination  I personally would keep the plants then in the greenhouse till March, then harden them off and set them out in April...
Your leeks can stop in  their seed tray longer, I leave my leeks till they are at  the
2 leaf stage  before moving them..

[springbok]

Theres a great video here on transplanting leeks.

Well I found it helpful :)

http://www.myallotments.com/MY%20VIDEOS.html