I've just posted a photo of the same plant growing here Chris..it arrived from nowhere!
Sisyrinchium is the name.

Yes, S. striatum. Bit of a seed weed.

Just as an aside, there is a variety Sisyrinchium stratium called 'Aunt May', has grey-green leaves margined with cream.

I love this but can't get it to stay /seed in my garden o(

There is a much nice yellow Sisyrinchium called S. palmatum. Herbaceous type like striatum rather than the alpine types.

Thank you everyone. I would like to grow it at home if possible?