Saponaria officinalis [speling iffy] or Bouncing Bet or soapwort.
Pretty but very invasive as it spreads by rhizomes. I love it but have to keep it in check

Thanks Seaburn. Often wondered what it was. It is very invasive, I dislike it and then when it flowers I think its not so bad. I guess in the right place, its OK. Certainly going to move it out of this bed as its swamping other plants.