I've opened a support ticket with Bigpipe as I'm certain the problem is at their end. It was working perfectly until 4 days ago when it just stopped. I'm in Homai/Manurewa on VDSL with a Draytek DV130. I eliminated the WiFi router being an issue by connecting direct to the modem via Ethernet.
Other than this, which is a big issue for me, it's been very stable for the 4 months I've had it.
Edit: There isn't a problem on the neighbour's Flip connection.