Can't be sure as they're not in close up but I think they're phlox

Definitely Phlox paniculata

Thanks. I like them, are they rare or difficult to grow as I can't remember seeing them before?

Not rare and easy to grow.

Lidle and morrisons both sell them in prepacked boxes. very easy, and most are scented. prefer full sun but will cope with a little shade.

And they like moisture at the root - if they are too dry, the leaves get mildew