Calabrase

I am growing calabrese for the first time and whilst they seem to have grown really well, I'm wondering if it is normal. It is plastered with flowers and I have plenty of bees about, but I can't see any heads forming. I have tried to attach a photo. Is there a chance it has bolted?

  Thank you!

May as well dig them up then and put something else in? Could I have done anything differently or is it just one of those things?

As above.

The heads must have formed if you've got flowers. You either missed them, or hoped they'd grow bigger!