I went onto feathersite and looked at the D'Uccles. It doesn't list cuckoo as an accepted variety, so I'm guessing they're still a project color. They did have some pictures of a pair there, and they're really pretty! I always seem to forget that not everyone here is from the US, and other...
Cuckoo Marans and Cochins both have feathered feet. I don't know if D'Uccles come in a barred or cuckoo pattern, I've never seen one (which doesn't mean much). If it's a bantam, I'd guess it's probably a Cochin then (maybe). What kind of comb does it have?