Thanks for the comments, they've made me revisit the schedule.

Our last LGW-GIB leg will be combined with a visit to the (future) inlaws in Andalucia so that's not so much of a burden.

Starting in ZRH and avoiding punative BA fuel surcharges is worth researching. I'm going to contact TA's in both locations and get comparitive quotes.

As for the SCL-AKL leg, glad you pointed this out. I'll book up early.