The run from Seattle to London also goes over northern Canada and Greenland, and whether you'll see the aurora on any particular night is hit or miss (recent solar flares, a tipsy magnetosphere, etc.). Check this website http://www.spaceweather.com/ before your flight for some idea of whether anything will be visible; it has a link to the NOAA space weather site, which also has a forecast of sorts. The view is about the same from the upper or lower deck.