Picked this up last night and the network team are onto it.
Looks like there are (were) two simultaneous issue going on.
Something with our network affecting some customers, and also unblock-us DNS went down at the same time.
according to this link (https://support.unblock-us.com/customer/en/portal/articles/2168719-open-issues-with-australian-and-new-zealand-dns ) the unblock-us issue is now fixed so if anyone is still having issues after a modem restart and changing to Bigpipe DNS please get in contact with our support team if you haven't already with as much detail as you can about the issue (i.e. post tracerts etc and whatever you have already tried)