Goosey:
The best thing here for the OP to do is take a look at both the LIM and property file for the premises (available from the council) and see if the property was actually legally consented for being partially used as a residential address.
That would then settle the arguments over if it is a "commercial" vs "free residential" install.
The property is consented as "mixed use," including accommodation. The unit has gone through the council/building consent process.
We ended up going with Orcon, and they'll do the install middle this month. It was on their small business plan, as they could do a price similar to a "residential" connection and it saved us the "hassle."
Thanks for your help everyone.