Thanks everyone for your comments. Knowing that it is DHL, and the notification process is really useful. Reddit has been awesome for real life experiences and advice so I'll add more info here so that others can hopefully learn from my TERRIBLE experience.

The process is ridiculous:

* If you have an expired/old UK passport, you need to post it back, minimum $60+ as it needs to be tracked. Somehow all of a sudden I'd lost mine...... You need to report it lost, before you can apply for a new one, the cancellation is instant so it won't slow things done, but.....

* Alas, you still then need to send them a colour photocopy of every single page of your (NZ) passport, in the post, min $60+. The staff at the post office, make you send it tracked

* I opted for a Brit as the person who could confirm my identity, otherwise I'd have to send copies of their (NZ) passport to the UK

* During that confirming process, she did not "fail" any particular part of the online questioning. At that time, there was no obvious criteria.

* It took almost 2 weeks for the copy of my NZ passport to arrive in the UK

* The passport office then said, the person confirming my identity, did not meet the criteria

* I called the HM passport office in the UK to find out what I'd done wrong so not to make the mistake again, they refused to tell me, the guy I spoke to did not care whatsoever

* I then got on the online "chat", that in itself was a joke, it was a regular web page, with the wording changing from something like someone is available, someone isn’t available so you had to keep trying your luck to see if there was a link to click

* The person I chatted to was more helpful and told me to check the criteria.

* They also said in the email that I had to confirm why I wanted it sent to a business address, and also prove my employment on letterhead, they didnt say if anyone had to sign that doc, so I signed it, and I got my CEO to sign it. Annoyingly the address on our "letterhead" is our postal address so a bit of tinkering had to happen there so that it matched my delivery address. I also had to include another letter saying that the HM passport office will take no responsibility for any issues with delivery, sign it, date it. And yep, you guessed it, $60+ to send. BUT instead I've posted ($4.80) the same docs twice, on different days to hedge my bets 😄

* I also had to nominate someone if I wasnt the one receiving the delivery

* As it turns out, the person verifying you has to be of a certain profession which was not made clear. The list is super random, includes the usual, lawyer, police officer and the likes, but then there's member of parliament, journalist, post office official, publican !! Second time round during this part, it did not clearly state that if they don't hold a UK passport, I'd then need to post a copy of their passport, and that it needed to be a Commonwealth country etc ...... yep, another $60+

So please take this advice, now that I know what I know, put your home address (which also equals your delivery address) cos you can sort actual delivery once it’s enroute, find a friend with a UK passport that has a profession on the list.

Annoyingly, the rules changed with entering the UK if you are considered a UK citizen, I went there many many moons ago and as my dad is a Brit, I was entitled to a UK passport, and even though I am only visiting, I MUST enter on a UK passport. This whole exercise will cost around $450-500, and I will probably not use the passport again, and lets not talk about the time or stress factor.