Difficult to tell what it is as can't work out which is the foliage that goes with the flowers. However, if it is an annual you can't take cuttings you'll need to collect seed or let the plants(s) self seed where they are.

Thx. I should have taken a pic a couple of weeks ago when it was in full flower. It does seed itself where it is but would like to spread it around the garden a bit as it is so pretty.

It looks like a double form of Sneezewort, Achillea ptarmica, but that's a perennial.

This looks like a perennial I have but don't know what it is. If its that you can split it in the autumn.

I agree with Landgirl that it's Achillea ptarmica 'The Pearl'. If you pull some bit from the side you will see that it has roots and will spread easily, it can become a pest. When it has finished flowering, just dig some up and pull apart, each piece should grow easily.

Glad I joined in - I know what it is now!