I think hot breakfast options are only offered on transatlantic flights out of LAX/SFO. UA 922 IAD-LHR is a day flight, where I guess you get two main meals in C (when I flew the route in Y, the breakfast was a small snack box, with a full dinner service before landing).
IMHO I don't see this as a *huge* problem because after all it's the middle of the night on your body clock when landing in Europe, so it's not like you have the appetite for a full breakfast. That said I don't like the croissants and wish they would offer something healthier or tastier, like the breakfast bread choices in domestic F.
Just to benchmark though I believe DL and CO offer hot breakfast options. Can anyone (who has actually flown them) confirm?