A few considerations - I see you are based in London therefore you will require a JAA PPL to fly in the UK. I am not sure if there are any JAA training schools out here (there may well be but I am not aware of any personally). The NZ PPL is an excellent license though with a similar set of emphasies as you would find in the UK. The main difference is training to fly in mountainous terrain, something we don't really experience very much in the UK. From what I hear, if you train in the South Island you will have much more emphasis on this mountain flying than you will in the North Island so this is something to consider.
The NZ Class 2 medical needs to be held in order to fly out here, and when I did mine, I was surprosed at how strict it was! My Class 1 initial in the UK was pretty much the same standard, maybe even not quite as detailed!
There are plenty of flight instructors around, and lots of aero clubs. In terms of airspace, procedures and weather etc, NZ is very similar to the UK. Also, the infrastructure for flying is very good. You would most likely need to do some training back in the UK after though so factor this in.
Below is a link to the NZ CAA - their website is an excellent source of info. Plus seach google.co.nz for aero clubs to get an idea of prices. Hope that helps.
http://www.caa.govt.nz/pilots/gettin...ence_pilot.htm