Onions ready for potting up?

Hi all, I sowed some big onion seed on boxing day into individual cells, I would like to move them into pots but the rootball isn't going to hold together as there are only a few roots, some roots are coming out of the bottom of the cells. Will they be ok to pot up or should I wait until a better rootball forms?

Thanks for your help, I am hoping to grow some large onions and would like to keep them growing steady without any check to their growth, I presume they will need a stronger compost before they are ready for the garden. They are currently in a seed compost. What do people think?

I have tried onion seed for the first time, mine are about 2" high now, how big should they be when I transplant them out in March ?

Final picture (24-June)

Excellent. Far exceeded my expectation - in the sense that I have always grown from Sets before, never had such good onions, and I had only one or two "bolters".

Mine were a lot later "dying down" than I expected, but that's about it.

Gonna wait till i get the coldframe heater up an running before i put mine outsside i reckon!