A slightly belated thanks to those who helped me earlier in this one. Belated, because after the nudges it took me until last night to actually twig and finish it off. A lovely, clever construction, and good clues, but put together it seemed to edge into chore.
Binks, I think all the answer you are looking for are in this thread somewhere, certainly how to deal with the unchecked letters, and once you have done that then the location of the third c should fall out.