To what FFPs can RBC Rewards points transfer?
If you end up with an award through an FFP that does not include the LON-FRA segment at no extra cost, I would probably transfer some points to BA, and then redeem for a "Reward Flight Saver" award for that segment. And I would not bother with Business Class on that short flight: BA's short-haul Business Class is pretty dire, with the same measly 30" seat pitch as in Coach.