Geranium pratense (meadow cranesbill), polemonium, and several of the salvias.

There are several campanula which grow to over 2 feet tall and flower in early summer

Try googling "Tall campanula"

Thanks, will check them out.

Lots of summer flowering gentians.

Agapanthus, eryngium, platycodon, salvia, or veronica. Also ceratostigma for very late colour

Hopefully for this year ive got a blue Dhalia,Lily and Phlox. ;-)

Lizzie

I have a tall growing campanula in my garden ...this one which flowers in June

http://www.flickr.com/photos/31559373@N00/4760887376/

I can send you some if you like.

If you're interested contact me via the private message facility

dwarf delphiniums......

Baptisia australis, blue Lupins like 'Persian Slipper', Linum, Linaria 'Canon Went'.

annuals as a stop gap can also be used effectively and some will self seed year on year; larkspur, cornflowers, nigella, phacelia, morning glory up a wigwam of canes.
cant think of any other blue perennials other than the ones listed.

how about globe artichokes but dont pick them ie let them flower . there such a strong focl point plant related and looking like a thistle . then when it flowers the blue is just fantastic . the bees love it too the point of appearing drunk and actuely staying overnight .

I've though of another - centaurea montana (perennial cornflower)

Thanks everyone, you have given me plenty to think about.

your welcome lizzie x .