Sweet rocket? If so, really good for bees and butterflies and very pretty too.

Yes like sweet rocket: Hesperis matronalis.
it is a lovely plant with white , pale pink or pale lilac flowers.

That's a pretty plant, it would look lovely in huge drifts, might have a go at that, so thanks for the name and idea!

My rocket flowered all summer last year. It's lovely though does sprawl a bit, like most wild flowers I suppose.

it seeds very freely and after 3 years of enjoying its spread I am now regularly weeding them out. I have 3 areas where they are allowed to flourish.