I have this. It's called "Snow in Summer" It's a perennial plant and in the dianthus family. I love the silvery blue foliage. It's a spreader and will even cascade over a garden wall. It's very good as a weed suppressor but can be a thug.

Cerastium tomentosum (snow-in-summer) aka Dusty Milller. Thug of the first water. Plant once and weed out forever.

Many thanks for your replies. Can I split/take a Clump of an existing plant elsewhere to plant in my garden or do I need to buy new plants?

Probably one of the easiest plants to move elsewhere that there is. Dig up a bit with roots and away you go.

It's easy to split & divide with an old kitchen knife and it's not horrible - not like poison ivy or that darn honeysuckle.