Onions from seed?

I should have added that I will be sowing seeds again, mainly Ailsa Craig, along with some of the ones I tried this year which were walla walla, to see if there is a difference in performance, I will also plant some sets as backup.
One other thing that I will add is that I read an artical which stated that as onions start to go to seed they give off pheromones which activates the other onions and starts them going to seed, so I will monitor them a bit closer next time and apply this to all my veg, though I am not sure if this is verity related or species as I don't think any of the sets started going to seed, but the bulk of them were heat treated