While I can get ORD-LHR flights, w/in your time parameters, for 11/1-11/3 to price out at the web fare of $458, finding upgrade(i.e., C) inventory for those dates is a bit more difficult, especially on the return. Outbound, AA 116, 122, and 132 (all JFK-LHR) have at least two "C" seats available. For the return, however, on 11/3, only AA 113 (LHR-MIA) and AA 141 (LHR-JFK) have any C inventory left. And when plugging in the former, the fare shoots up to $1300(!), and the latter flight (AA141) leaves LHR too late(8pm) for you to make a same day connection in NYC, thus necessitating an overnite there. Good luck.