May I suggest that you avoid mixed packs of anything or else buy them from a reputable wildflower supplier. Those euphorbias are indeed wildflowers but not anything like as desirable as ones you choose yourself. And they seed everywhere.
If you haven't come across the Meadow Mania website, why not have a look it? I bought a few packets of annual wildflower seeds from them and they sell mixed packs as well. I didn't go for a mixed pack because it contains seeds of things that I already have in abundance. My cornflowers, corn cockle, corn marigold and poppies gave a lovely display this year. I did allow some of those euphorbias to stay that just popped up uninvited, but not many.