Aaaarrrhhhh.... harden up ya pack of sissies! How do you know what sorta clothes you will have to wear outside in the mornings if you don't have the old handy indicator of frost of the duvet?
Most houses do have insulation...later houses anyhow, and all new builds have ot have Batts installed in the walls etc (Pink Batts...fibreglass padding).
Getting the roofs done? Easy enough, even on old houses, they have this stuff they just spray/pump into your cielings, really keeps the place nice (We put it in here decades ago)
Double glazing? Never seen it here.
Central heating...well.... my Dad, being a Cannuck, was horrified like many of you to find kiwi homes so cold, and when we fianlly settled in this place (family home, here for the last 50 years!), Dad had a commercial deisel heater installed. It is great, really warms the place up when it is on...trouble is, the tank holds 600l, at around 90c-$1/l for heating oil (more than ord Deisel as it has kerosene in it), that lasts for around 3months .... makes for an expensive warm house.
Because it is such a damp climate though, what DOES help enormously is to have a dehumidifier... without actually heating a house, they sure make it far more comfortable!
I tihnk another reason our houses are cold is that we have quite large window areas in most houses, and as you say, no 2ble glazing....
Same climate as old blighty?? Hey, could be,but a LOT less gloomy in the winters...longer days, more sunlight hours, makes it a little less depressing than the Pom winters. And if the weather DOES get to you, hell, $1,000 gets you a week in fiji for a break away....
cheers, Stu.