Probably a mix up with the packaging where they were purchasded from by the garden centre

The daisies just came up from wild seeds in the soil, if you mean WILD daisies like occur in the lawn. All that has happened is that for some reason your nigella and poppy seeds failed to germinate.
This could be for several reasons.
1. Garden centre seed is often stored in a 'greenhouse' type building which heats up in the day and cools down a lot at night, so the viability of their seed packets can be affected if the seed has been there for some time. It's always better to get seed from mail order or a shop in a 'proper' building, for this reason.
2. More likely, your seed drill dried out at some time during the seeds germination process. Wet and cold weather alternating with hot and dry weather will often rot seed or cause it to fail. The only way to be sure is to sow in a drill which you soak well with water before sowing, and to cover with a light material like sand. If the weather stays dry, make sure you water often.
Nigella self seeds everywhere so I'm surprised that has failed. Some poppy varieties are fussy, but wild poppies similarly come up easily.
If you've still got any of the seeds, try sowing a few of each on damp kitchen paper on a shady window sill (out of direct sunlight) see if any of them show signs of germination after a week or so. If they don't germinate, you will know it is poor seed.

Thanks for the responses. Nickt08 - I thought about the mislabelling option but it the odds would be astronomical (perhaps I should do the lottery???!)

Bertiefox. 1. sounds a possibility, though the display was in the main building. Still, a logical explanation.

2. The conditions were indeed changeable...remember how chilly May was? so germination failure also v possible. I never thought of that, being a beginner.

It just seems really odd that the 'wild' daisies flowered where I'd set up my drills and sowed my seeds. It's like something out of the X Files! There has to be a logical explanation and I think yours is 3/4s of the way there.

Thanks again *sighs, puts on gloves and starts intensive weeding*

If the daisies have come up just in the drills themselves, not in the whole area where the soil was disturbed when you prepared the ground for sowing, then THAT is weird. That would make it sound as if the wrong seed somehow got into the packet, but as you say, it's hardly likely to have got into TWO wrong packets.
Being optimistic, it's still not too late to sow nigella and poppies, or 100 other hardy annuals which will give you a good display. Good luck!

sowed a a seed selection which apparantly, s attractive to,. bees.The annuals came up some obviously wildflowers and at first they looked like weeds,but when now in flower do attract bees and look good, theres even a couple of nettles in there whether they purposely in or like the daises found their way in I dont know

Glad you've got a nice display of flowers now for the rest of the summer, Chega.