Aw shame... I had an option on flights to Vancouver for £450 per person including tax ex Glasgow for the last week in June 2015 once the Scottish schools finish up for the year. Couldn't believe the price but it was on launch day for WestJet. However, we reckoned the Vancouver temperature would be the same as Scotland for that time of year so passed up on it.
There have been some fab flight prices for 2015 ex Scotland compared to 2011, 2012, 2013 and 2014 and I am paying less than I paid in 2011 to go to America this year.
Have just looked again on Kayak across August out of London to YVR and see prices from £550. Might be worth you looking again. Wed and Thurs departures are cheaper but you might not be that flexible.