Perennial plant ID

Hi everyone,

Does anyone happen to know what this plant is please? It was photographed from a bit of a distance as we were sat in the car in traffic, so apologies for the quality. The flowers are actually a light purple colour. These plants always reappear in a garden we often drive past and they seem very happy there as they are in several sites around the garden. They also line the front of gardens near a seafront area (if that helps). 



Thanks for any help,

Lucid