Pretty much every tourist flew in, and tourists are in close proximity to each other for 4+ hours. It doesn’t matter how often New Zealanders fly internationally if tourists come in infected. The UK has international flights that last a 15-20 minutes. This could give you covid for sure, but it may avoid infecting the whole plane.
A total of about 3.8 million tourists arrived in NZ in 2019, a number equivalent to about 75% of NZs population. The UK had about 38 million tourists in 2018 (most recent numbers available) and that equates to about 56% of the UKs population. NZ had a lot of tourists relative to its population.
https://en.m.wikipedia.org/wiki/Tourism_in_New_Zealand
https://en.m.wikipedia.org/wiki/Tourism_in_the_United_Kingdo...
Even now we are getting people fly in with covid every day, usually several cases and this is happening without there being international tourism anymore.
The UK doesn’t even require self isolation in all cases and having tried asking people to self isolate in NZ, we know exactly how it doesn’t work. Managed isolation is hard enough to get right.
https://www.gov.uk/uk-border-control
Overall, what happened in NZ was impossible in the UK due to a lack of will, not anything else. NZ was willing to sacrifice it’s largest industry. How would you describe the approach used in the UK? It doesn’t appear to have a particular focus or goal.