Like you, OP, I've lived in NZ for over a decade. I would like to return to the UK but DW (not from UK or NZ) is not interested. I miss my family terribly, and do feel my children (born here) would have a more fulfilling upbringing in the UK. Originally, our agreement was that if one of us wanted to return, we'd pack our bags and go. However, when it came to it, she changed her mind. The objections kept changing and the goalposts kept shifting. She just wouldn't countenance it. It was very frustrating. However, the conclusion I came to is that a change as big as that requires her consent which she is entitled withhold. I do not suggest that you should take the same view. It was just something that helped me a bit.
Unlike you, I've never received physical abuse from DW. Emotionally abuse? On the basis of what I've read on MN ... yes, she can be emotionally abusive. I ended up self-harming for a time. However, I have found ways to cope, and as I am the sole breadwinner I am in a relatively secure position. I suspect her of having undiagnosed ASD, and I often feel very lonely.
In the last couple of years I have been back to the UK with the kids on holiday, and while it is clear that some things have changed, to my mind it is demonstrably still the same place. Being back there is like putting on an old, comfortable piece of clothing one has had for years. I do not think I will ever stop missing the place, or my family, and I do regret my decision to come here.
My experience leads me to say that whether you want to return to the UK and whether you wish to leave your husband are entirely separate issues, although in situations like these, they do get muddled up together as they both cause you unhappiness. You should deal with them separately. The unfortunate fact is that regardless of whether or not you separate, you face real complications in getting back to the UK with the kids. Do note that if you travel back, you will be asked at passport control whether the other parent consents to the children travelling to the UK and the reason for this. I was. You would have to admit that he doesn't, or you would have to lie to the passport officer. Either answer could land you in terrible difficulties. I second the advice given by others that you talk to a lawyer.