As per picture above, our new neighbour just moved in and his house shares boundary with three houses - A, B & C. My house is B. All properties are freehold title. 

House A owns the land that has part of the shared driveway, but they don't use the shared driveway at all - the house is linked to the road.

There is a retaining wall (about 1m high) along the shared driveway, our neighbour being on the higher side.

The current fence is a wire-mesh fence like this one. It's about 1m-12.m high. I think its condition is adequate but the new neighbour wants it replaced.

Our new neighbour wants a new 1.8m wooden paling fence along the shared driveway.

My questions are:

1. Do I need to contribute to the cost of a new fence? I think the fence is adequate (there might be a couple of small holes but it's at least repairable)
2. If I need to pay for the new fence, how much do I need to pay? Does the owner of house A need to pay? He doesn't use the driveway but owns part of it?
3. In regards to the height of the fence. Normally you can build a fence up to 2m but our house being on the lower side of the retaining wall is already 1m lower, if we put a 1.8m fence that'd be 2.8 meter fence for me. I couldn't find anything on Auckland Council's website but this is what I could find online. Which side of the retaining wall do you measure that 2m height restriction? 

From here, and here

Any fence on top of, or a part of, a retaining wall. If the whole is over 2 metres, but less than 3 metres, you will also need your neighbour’s consent.

Thanks for reading!