Leycesteria Formosa.

Yes I agree, its a nice shrub but does sucker a bit.

And self sow.

Where can I get one?

Many garden centres will stock it. Alternatively, find someone who already grows it - there are bound to be seedlings cropping up nearby.

Thank you all. It was growing on the side of a cycle path. I've cut a branch off.....would I be able to grow cuttings from it?