Air Berlin, Edelweiss, and Condor all fly to/from YVR and have one way fares, often quite attractive especially at the start/end of the season (May, and September/October) I know that may be too late for your purposes, however.
Virgin Atlantic is flying to/from YVR as of May, so that may not help.
But there are charters which fly, such as Air Transat. I have no idea of their routings/timetables, but it may be worth checking.