Layla Jade and Angela Long are 2 that spring to mind. Not frequent, but they have both used the 'c word' on more than one occassion.
FWI worth, some of the american performers who use it are Jeanna Fine, P J Sparxx, Chloe (Nichole), Stephanie Swift (couple of times), Candy Apples, Ginger Lynn, Jill Kelly, Tianna, Madison, Alexandra Quinn, Annette Haven, Felicia, serenity. Actually it would be easier to list the ones that haven't.
Another aside - mainstream actresses\celebs who have used it: Amanda Donohue (Castaway), Holly Hunter (Jesus' Son), Jodie Foster (Silence of the Lambs), Julie Christie (Shampoo), Margot Kidder (unknown), Joey Lauren Adams (Chasing Amy), Leslie Hope (Bauer's wife in 24 in the rather explicit Paris, France), Adrian Shelly (can't remember), Kim Bassinger (indistinct in Fool for Love), Denise Richards (Wild Things), Caprice (Richard and Judy:)), Carrie Ann Moss (Memento)
Apparently Demi Moore used it in G.I. Jane, but it was cut from the final release.
Not that I'm an expert or anything:)