La Puce writes

. Though I wouldn't
worry planting V. bonariensis and marguerite in a garden.

Nor would I. But I wouldn't plant them in the wild, and if I wanted a
patch of UK natives in my garden I would not include them. If otoh all I
was after was a wild look, then I wouldn't worry. And that was the
distinction I made many posts ago.

. I do
think Spanish Bluebells are pretty, but I am a firm beleiver that the
more flowers I plant in my garden, the more prolific my garden becomes
in insects and birds,

That is the logic I do not follow. If the plant from different habitat
that you are considering planting will support only a small number of UK
generalist species, which already have abundant food supply in your
garden, in what way does planting it help make your garden more prolific
in insects and birds?

By all means plant it in your garden because you like it, and it adds to
your variety of plants. But if you are planting specifically to extend
your range of insects and other fauna, it makes more sense to plant
either a UK native or something closely related from N Europe.

--
Kay