I'm going to close this with the status "issue resolved".
I've verified all issues related to speed have been sorted on my own network and other networks (including @SamF). Services outside of 2degrees can, and will always have problems and this is the world we live in - NZ has incredibly good broadband and so "speed issues" are seen more frequently now when really there isn't a problem. Regardless, even with the Speedtest result we still beat Australia's NBN.
In conclusion - testing via Speedtest is no-longer a viable means of testing especially when the destination is a bit further away and the user is on a Gigabit connection. I don't know what has happened, but Speedtest has actually turned to crap over the last year. Just simply don't rely on this. If you believe your connection is truly under-performing and you can prove this outside of Speedtest and testing to multiple services then by all means call your ISP (this is a general rule) and get them to investigate.
Good job @NickMack - love your work. I'm putting this to bed now.