I wouldn't bother with Turners, the one in Chch is not really an auction house and more of a dealership that drives its cars past a small rather bored audience. You can easily go an hour or more without anything selling and most of the same cars will come round the next day and so on.
I reckon now is the time to buy from a dealer and to push a really hard deal. Some of these guys are starting to hurt and they need cashflow to pay the bills. I'd take 20% of their sticker price and call that my maximum.