This school that you are looking at are a very good school, I have been there on several occassions and they always come across as a very professional and well set up company. They are attached to the Canterbury Aeroclub which has been around for a very long time and are well thought of.
If you were to go down this route you would come out with a NZ CPL/IR which is an ICAO licence. To convert it to a JAA CPL/IR you would have to sit ALL of the ground subjects upon your return and then sit the JAR CPL and IR skills tests. Because you already have a CPL you would get away with training as required for the CPL skills test. Because you would have the IR you would get dispensation to do a 15 hour IR in the UK instead of 55 hours.
I would allow around another £10,000 to get you converted, obviously this would depend on you doing everything in minimum time, so don't be surprised if it costs more.
The only thing to be wary of is the NZ CPL test is radically different to the test you sit in the UK for a CPL so you will definately need 10 - 15 hours back in the UK before attempting the test here.
Overall the NZ option won't save you any great amount over the traditional modular route once you take into account travel and accomodation. BUT you will have a great time, experience things that you just don't here e.g. Low Flying, Mountain Experience and you will end up with 3 commercial licences. JAA, NZ and AUS (you can get the australian licence converted purely on the strength of the NZ one.)
Hope this helps.
