Did you try looking at what prices you could get with http://www.itasoftware.com ?

I have often seen the situation go the other way - people from Britain seem to get cheaper flights!

I'm sure there are other solutions, but if you don't mind going to YVR instead, there are several cheap charter options.
http://www.flyzoom.com
http://www.canadian-affair.com
http://www.airtransat.com