1. Is there an active aquatic club in Western Bay of Plenty - I've heard it is no longer active - anyone know??
Yes there is. Answered in the previous post.
2. The pond is full and being filtered, but is bare of plants and fish. What should I do first? I've been told to get a few plants and a few fish and build up slowly.
A pond that size you can add both plants and fish together. The fish will be happier to have places to hide in the plants though so might pay to add them first.
3. Do I need particular plants other than my planned lilies, for pond health? I think I have plenty of surface area of water for fish oxygen supply. I have seen frequent comment about 'oxygen' weed. Do I need this?
You do not "need" any particular plants but those described as "good oxygenators" are useful. Read the labels on the plants on the shop as they will have this written on them.
Oxygen weed is a good oxygenator (hence the name) and can be gathered from local waterways. be careful not to gather any with weeds attached.
4. What is a WCMM? Lots of mention of this fish, but I don't know what it is.
As stated - white cloud mountain minnows, Tanichthys albonubes. Not what I would recommend in a pond as thay are hard to see.
5. If I get a few 'goldfish' from a friend, and he has 'blanket' weed, will I inevitably get this weed too? Is there any way to avoid getting it?
Yes
6. Should I get equipment to clean detritis off the bottom of the pond regularly?
It would be handy. I haven't got any for my pond yet (about 6,500L)
7. Once the pond is running and I have fish and plants in it, can I just top up for evaporation loss from the tap, or do I need to treat the added water somehow before I add it? I'm presuming the water here is treated with various chemicals.
This varies depending on your water source. I don't add anything to mine as we don't have chlorine etc added to our water. In a pond that size I don't think topping up with water that hasn't been dechlorinated will be a problem.
Make sure your lilies are not splashed by the water feature as they do not like this.
Got some pics of your pond? 8)