Hey Greenfox
You seem to be looking for a school that trains in H300's.
Don't worry about what machine you train in, even if it's a Bell 47, that's where some of the best drivers started...
Experience is experience. If you want to fly mainly H300's, what does it matter when you go back to Ol Blighty that you have R22 time in your log book?
I have heard from Oz good things about flying in Wanaka and I can only assume that they mean Simon. (See earlier posts). If I want mountain experience, that's where I'm going. (Plus the trout fishing is legendary)
You asked which companies in NZ have a good reputation in the UK. Ask people in the UK, don't ask in NZ! Ask the person that you want to get a job with who they recomend, they are the one you are trying to impress.
If it is a PPL that you are chasing, then go with the school that has already been recomended. You can add endorsements later if you want to fly a particular machine. The only hassle is not having 100 hours on type for insurance purposes if you try to privately hire it. Again ask the company that you will hire from what their stipulation is before you train.
Just food for thought. Good luck.