Berberis thunbergii ‘Golden Torch’
This is part of the RHS trial and has a lovely upright style of growth. I have not been able to find it in New Zealand but the Polish variety ‘Maria’ is similar and available here. I’m not sure if beheading this to force it into a hedge will bring out the best in it, and of course you will have to contend with prickles! Being deciduous, there will be bare brown branches through winter, but what a cheery glow in spring.