Yeah, I was slightly ambiguous in my question. I have not actually submitted the passport for renewal yet. Considering other options that just occurred to me, because I cannot get an appointment at the embassy for some time. Yes, I'm aware the previous passport would be voided, but I was unsure if a voided passport and a new one could be used together (this sounds the best option).
2. That's a bugger. I did ask immigration, but got a confused look. I had never been given a term shorter than one year before, even when I changed passports.
3. Right, this would be the option to leave it all till later. The question is really whether one can travel on less than 6 months' validity.
Thanks!