17:30 Sunday and I'm still suffering - <1.0Mpps. SA44. Not fixed everywhere yet - or just me?
Try powering down your router for about 15 minutes and try again. This should force your connection to reconnect with a different session (as I'll call it), which could be why you are still having an issue.
When my connection restored to normal speeds yesterday at ~7:30pm, my external IP address had changed, thereby indicating that plusnet had forced me to reconnect with a different session.
You could also check your external IP address before you power down your router, to see if it alters.