I do believe the cone shaped ones are spent flowers and should be snipped off to encourage more buds, its ironic im sure i saw monty mention this very subject on gardeners world last night. ;)

yes he did, its just i've got a lot of the cone shaped ones on mine and i'm sure they aren't spent flowers, i really shouldn't doubt monty but now i've got a second opinion... wheres the scissors. thanks windy

Flower buds on Dahlias are round or slightly flattened, satiny looking, and with a "crown" of bracts between the stem and the bud. They usually face downward at an angle until they are almost ready to open.

http://image.shutterstock.com/display_pic_with_logo/4028/4028,1283373014,1/stock-photo-yellow-dahlia-flower-and-bud-against-a-blue-sky-with-clouds-background-60190393.jpg

The seed heads also have the crown, and face downward, but the thicker bracts form a cone, shaped almost like a peperoncini:

http://images.mooseyscountrygarden.com/gardening-journals/garden-journal-06/dog-dahlia-seedhead.jpg

And:

http://www.flickr.com/photos/nimart_example_ad/4048067330/

thanks again