Onions - from seed

I am growing mine from my own seed this year, the year before last I selected the two biggest bulbs from my batch and put them both in a fertile piece of ground and left them to it.  They grew into two huge plants last year and I harvested the seeds when they were ripe.  The seed heads were riddled with onion fly maggots so it was not nice separating them but I did not want to let them carry on and pupate. 

I sowed a batch of seed the last week in December in the unheated summer house, and they were at the crook stage a couple of weeks ago when I then transplanted into plastic drinking cups and put back into the unheated room.  They have survived the cold weather quite happily, as have the sets I planted in pots.  I will transplant them out into the lotty when they are about pencil size and when (if) the lotty dries out a bit.