It's terrible tonight, and I see PN service status is reporting some connectivity problems, so I don't know if it's all part and parcel of that, or if it's specific to my connection.
I'm seeing random, brief disconnects, and when it does stay connected, I'm getting speeds more on a par with dial-up (I've got ADSL, but not fibre).
The support page says a single router reboot should fix it, but I've tried twice now, with no improvement.
Outside support hours now, and whilst they will be able to log it tomorrow, I doubt any action will be taken 'til Monday.