Another factor to consider...
if you are in paid J, you will have access to the Signature Lounge in YYZ which includes a nicer food selection than the Maple Leaf Lounge including a la carte dining. It would allow you to skip the meal on your LHR flight if you wish, but you would want to spend at least an hour in the Signature Lounge.

PS which date are you flying? I picked random dates in July/August and the earlier flights YYZ-LHR are on 789 not the 333.