onion sets or just small onions

Hi Everyone
I decided to sow some spare red onion seeds in a tray and see if I could use them as spring onions earlier on this year. They grew well enough to a point, and I did use some as spring onions. Whats left have stopped growing and bulbed up slightly, about the size of the onion sets I bought this year.
What I would like to know is, as they are crammed quite close together, can these be pulled up now and dried and then used as sets to plant in sept or march/April. I'm not sure if they need a dormant period or cold period to grow properly

Any help gratefully appreciated