Phlox paniculata whilst not 'fluffy' are very good. Liatris spicata seems to attract them. Eryngium are more blue as are Echinops but a good and different shape. Don't forget Hebe and Buddleia.
I will continue to think about this.

Brilliant Eileen, thank you. I wondered about Phlox because they’re quite long flowering (I think), and I do like them, but will Google Liatris and Eryngium. Not keen on Buddleia but of course butterflies are!

Sheila, the smaller growing buds are much nicer. I have one called ‘Pixie Blue’ which I love. I find that butterflies are very fond of Thyme flowers and also the late summer flowering stokesia laevis.

...also...Sedums of course. The most purple one I have is S. Thunderhead, and Jose Aubergine is another good purple one. But the prettiest is Red Cauli. Some of the smaller, trailing ones would fit really well into your colour scheme...S. Cauticola and s. Carl. Verbena bonariensis is a great butterfly plant.

Hi Sheila! Happy New Year. You've just described my Little Joe Pye Weed (Eutrochium purpureum). I've only had it for 1 season and I can already say it's a keeper. It's in the mint family, has lovely bluish green leaves, begins blooming mid summer and continues on through frost. It's all about butterflies with huge mauve, flowerheads that are fragrant and long lasting. The swaying seedheads is a food source for wildlife over the winter. It wants full sun but no fertilizer. It prefers lean, sandy, gritty soil with good drainage. Little Joe grows to about 4 feet. Regular Joe Pye is better suited for the meadow. Newer cultivars are now available in various shades of pink, purple mauve, dusty rose. An excellent addition to the butterfly garden or border.

Here is a link to mine
https://growsonyou.com/question/show/322300

Thanks very much Karen and Paul for your suggestions,
especially the stokesia 🙂 .

I am going to try the Eupatorium in my wild area behind my greenhouse.

Eupatorium certainly attracts the insects but my native one had 'Elastoplast' pink flowers and I decided it could be replaced with other 'prettier' flowers.

Any of the Verbena's will be good, I forgot about the brilliant V.bonariensis and I have loads of it. Veronica spicata and its allies are tall spikes of flowers that also come in the colours you fancy. What about Centaurea there are many purply forms instead of the usuall blue spring flowering one?

I also have a Eupatorium with dark leaves and pretty white flowers. Yes, Centaurea is a good idea, and I do have several varieties of Verbena, all with purple flowers (v. Santos, V. Seabrook’s lavender and V. Bampton which is lovely and ‘starry’.

Thanks again!

I'm not keen on the Buddlea or butterfly bush because of it's somewhat mangy appearance. Also Joe Pye is a late season bloomer, so maybe you want also get early season bloomers.

for the later season consider asters [many have been renamed as Symphyotrichium ] lots of heights and colours.

I have 2 more suggestions I know are superb plants for any garden.

Yarrow
Achillea millefolium 'Pink Grapefruit

Astilbi Queen of the Prairie

I love Asters, Eileen, thanks for the reminder.

Thanks Paul, I will check those out (I know some Achillea but not that one).

. . . and Astilbe queen of the prairie looks fluffy - lovely 🙂.

LOL yes, very fluffly.