I have a very old 'paradise.net.nz' domain currently controlled by Vodafone or Clear.net or Paradise.net.nz

The (busy 24/7) Linux server for this domain is located and managed by me in my office on a static IP that won't be changing.

I'm trying to get a current UDAI out of Vodafone to transfer this domain to Metaname where two of my other domains reside. 

I do not want any downtime on this server if possible.

My primary issue is that trying to get any sense out of Vodafone at present is a nightmare and I have been told that I have no access to a domain control panel to allow me to change the name servers prior to moving the domain.

It appears that Vodafone immediately disconnect DNS when a domain is transferred away from them. However with this old paradise domain, I have yet to get a straight answer about the ramifications of attempting this.

Plan A - Is that I set up a zone with Metaname (that still points the A records at the same static IP, but uses Metaname DNS) a day before attempting the domain transfer to them, then execute the transfer.

Metaname has a procedure to do this but they mention that the name server records should be changed on the original domain an hour before executing but I have no access to those settings via a control panel.

Will I have a downtime outage if I just go ahead and transfer without changing the paradise name server settings?

Any other clever plans gladly accepted.

Edit: Clarification - It is just a registered .co.nz domain with VF. There is no hosting involved and only an mx record pointing at the soon to be stopped paradise.net.nz mail