They are Rockery Daisys :o))

There are some called.....
"Erigeron karvinskianus" not sure if thats your one though?

I agree, and it's one of the most useful plants in the garden. Spreads slowly and establishes itself in cracks and walls, and flowers for months. Lucky you, getting it as a bonus!

Lovely plant, also known as Pulborough Daisy. As Landgirrl says, it can look after itself, seeding and spreading but is never a nuisance!