I once had to implement excel-equivalent UI functionality (resizable columns, etc) - using javascript - which needed to be compatible on both Netscape and Internet Explorer. Early 2000s, before jQuery or even prototype.js.
Which is another way of saying, don't talk to me about being tired of javascript...
They're probably running fibre cabling for the same geographical distance as here considering NZ is slightly larger in area. So yes, it's 20 times the premises, but I think calling that 20x the cost is a bit of a stretch. You'd have have to calculate the additional cost from street-to-house for the additional 19 million premises versus the difference in running the cable the length of each country to prove that 20x number.
Side note: just left BT. Hate their service, never go back.
Which is another way of saying, don't talk to me about being tired of javascript...