Not sure if it makes a difference - as transatlantic routings vary, but my CO flight to MAN from EWR a short while ago landing on 6R came in straight over Dublin and over the Mersey estuary form memory.
Couldn't tell you about outbound to EWR from MAN though, because it was cloudy and I couldn't see the on-screen map from my seat.
As far as on-line checkin with BA, get an legroom seat by the window if you can - front row of Y class or by a door.