IMO:
Iīve done the AKL - UK trip a number of times and just about everytime with different carriers and always in Y. Hereīs a breakdown of my impressions:
Cathay : Horrible. A pot noodle as the main meal with what I found to be very cramped seating at the back of the 340īs.
Garuda: probably not an option at the moment but probably one of the best trips. Loads of delays due to US Ac. In flight eng shutdown on the old DC-10. 747 ceiling panels falling down on take off and landing. In all a 2 day trip took 5 days.... If you have plenty of time and are flexible you get a few additional stopovers.
QF & BA: IMO canīt beat the Y product of BA. QF on the other hand left a lot to be desired. Ok it was 2 years ago but it felt like the 80īs with a snack bag instead of a meal and no PTVīs.
Korean: Not the best not the worst. Safety side of things appears to have improved no end after the technical advice given by Delta (?). Iīd not even consider the safety issue when booking a ticket with them.
SQ: Probably the closest to BA in terms of quality and service. If the price was close Iīd choose SQ only to avoid the hassles of entering the US at LAX.
JAL: Great. Limited English programming but great food and a lot of emphasis on service.
Best trip ever was with CO when they still served AKL after a 1 nite stop over in HNL. Shame they didnīt carry on with the route....
Hope that helps in some way. If you need anymore assurance I work in Ac maintenance and am resposible for a european based 6 ac fleet of widebodies and would fly Korean.