I believe Op's father is Flex, while he is PY lowest. Regardless it's t-5 days, but it is only 16 eUps if high flex. Given the ticket is in March though I doubt it's high flex.
Latitude also has no co-pay incidentally.
The other option is of course LMU; prices from YYZ->LHR, which is shorter I've personally seen $680 - $4300. From the LMU thread I don't foresee YYC->LHR as likely to fall outside this rather broad range.