Should have also said, when you go to My Account > Technical Checks where it will under take a health check on your line, does it show a green tick saying everything looks fine and if so what down & up speeds does it say on screen.
Or does it show a red message that there is a problem with the broadband ?
You could try some of the basic stuff, like reboot the router, press and hold the reset button on the back of the router and leave the router switched off for about 20 minutes.
If that doesn't work and there is no improvement in your internet speeds, then contact the nowtv broadband team who can assist you further.
There might be a remote possibility that open reach haven't switched you to the top tier superfast fibre where you are stuck on std fab fibre ?
Go to My Account > Broadband & Calls and under moving home there should be a telephone helpline number.
Just be aware that their phones lines have been busy for the last few days (according to the red service banner on top of the forum pages).