Collecting seeds

The problem with sowing anything direct is that you have to sow hundreds, or even thousands, to ensure enough will make it. It's why so many plants produce such huge numbers - foxgloves are a classic example. Also, some are more vigorous than others, so you can end up with a large area of just one thing, rather than the nice mix you're hoping to have.
If the ground and conditions aren't suitable [that's the problem I have here] then it's a waste of seed too, as a lot of it rots/blows away or gets eaten.

 

My ground is just too rough and clayey to sow direct.

I do like to buy the assorted seed like annuals or balcony mix from Chiltern seeds. Then I sort the seed out on a tray and sow in small cell trays and they will stay in these till planting out. I love the guessing what it is.

 

Thank you @fairygirl and @infradig never considered them getting eaten and I agree, I don't want too much of the same.