Hi, I've not been to Invercargill but have seen the weather reports and spoken to locals. I believe it is of a similar climate to the UK in the summer and very cold in the winter. Whilst the weather is still reaching good temperatures in the north island, it is snowing in Otago region (north of Invercargill). Central heating is rare and you have to watch when finding property that it is well insolated. Further north on the S Island, Christchurch, the summer is hot and the winter cold. If climate is an important factor to you, you will probably find Invercargill a little too cold for you. Hope this is of help.