Population of NZ >10x less than UK, UK is a European business and financial hub. NZ contained their limited number of cases very well, UK had to mitigate against extensive community spread.
The problem for NZ is managing their borders going forward. NZ is a country that is massively dependent on tourism. It is the country's largest export industry in terms of foreign exchange earnings and directly employs one in eight New Zealanders. No one is going to want to go on an adventure holiday to the land of Hobbits if it first means spending 14 days in a hotel room eating room service.