Stick with going through YVR unless you can get on an Airbus plane. The YYC-LHR runs use mostly (exclusively?) CP 767s that have NO PERSONAL VIDEO.

While others find the seats comfortable, I find the old CP seats very UNCOMFORTABLE. The foot rest does not seem to come up as high. While there is more personal space (seat pitch), I prefer the Airbus series or AC 767s (non 3000 series flight numbers).

I had a choice of only CP 767s on my return flight from LHR yesterday. Service and food was good, but video sucks, even the projection equipment is fuzzy and dull. If you don't care about entertainment, then you will be ok on 3000 series flights