Unless your line of work is construction-related, Christchurch may not be the best choice.
I have friends who moved out there about 6 years ago in their mid-20s, both working for PWC and got transfers to Auckland. They love it out there but they have young kids and enjoy the lifestyle. They've not seen that much of the country though, and for all the "we can go skiing, and mountain biking, and..." stuff, mostly it's about the same time to get anywhere to do those things as many places in the UK. Great if you like boats though.
Conversely, my gf is from Auckland. Has been in London 10 years now, left NZ as soon as she'd finished her degree. Not that she doesn't like NZ but she loves living here, has gone through various visas and the UK citizenship process and is in the process of getting her passport. The sheer choice of stuff to do and see is amazing in comparison - and there are dozens of other fantastic cities that you can see for a weekend via a cheap flight or train.
I've visited Auckland a few times and I'm not sure I'd want to live there. It's as big and sprawling as Greater London but with way fewer people and about as much to do as a provincial town.
The key thing is, as NZCol alludes, what are you looking to get out of the move? What do you think will be better about life over there?