Onions from seed?

I sowed onion seed in February, the first for a long time, they were sown into modules to save having to prick out and planted out mid April and a week later I planted out some heat treated sets, as well as normal sets, a high number of the onions from seed started to bolt and that was towards the end of June I think due to the hot weather and the fact that I didn't water, the sets were OK, I still got a reasonably good crop from the onions but most of them from sets, the growth of all the onions was cut short due to high winds and torrential rain which flattened everything.