I took a punt on one of those seller refurbished 5Cs, on eBay, as a temporary solution to a work phone problem. Trouble is, it's arrived, is in pretty good shape (and good working order) but, at the moment, no 4G, at least where I live. I think it should work, but would like to verify my research. I've: 1. Obtained the model, from the back of the phone. 2. Visited Apple's LTE page. 3. Verified that this is the model sold by Sprint, in the U.S. (A1456) 4. Checked it supports 800DD, which is what O2 UK claim to support. What I've not found is any actual usage cases, or if Apple and O2 are talking about the same thing when they refer to 800DD.