I'm loathed to contact the help desk, as when I've had similar issues in the past they were generally little help and members of this forum (who work at Spark) were able to sort the issues far more quickly. So I'm hoping that might be the case this time. But I don't remember who the users were.
I'm on Unplan Fibre Max and just discovered I'm only getting about 120 Mbps down and 140 Mbps up using Speedtest.
I'm not sure how long it's been like this and only noticed because I recently re-setup my WiFi and noticed those speeds maxing at the above level, so I initially assumed it was a WiFi issue. But I decided to do a test from my PC over ethernet (which previously got 960 Mbps up, 540 Mbps down), and found I'm actually getting the same low speeds over ethernet as well.
If anyone from Spark watching these forums who could help would be really appreciated.