Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
"many of them need to transit in Heathrow, thus resulting hefty airport charges & taxes"
Nope. Airport charges and taxes for transiting LON are modest. What you are seeing is the effect of massive YQ surcharges imposed by BA on long-haul flights. Here are your low- or no-cost options to get to Europe from YYZ:
1. Call BAEC and ask about award availability on EI's YYZ-DUB service. Very low surcharges on EI's TATL service, but ba.com cannot display EI award availability.
2. On ba.com, check award availability on AA YYZ-LGA/JFK/ORD, and AB availability JFK-DUS/TXL, and ORD-TXL. No surcharges on AA flights within the Americas, or on AB flights worldwide. (Note that you would have to book the AA and AB flights as separate redemptions, lest BAEC's more expensive multi-partner redemption chart kick in.
Good luck!