I was with NowBrodadband for four years and also convinced my relatives to join up too. I never once used their supplied router and neither did my relatives.
Use either a Zyxel VMG1312-B10A or Zyxel VMG8924-B10A and set them into bridge mode to connect to your vDSL wall socket. You can buy them cheap used from eBay (I bought mine for £10-£15 each) - Other Zyxels may work too, but back in 2015/16 those were the best around at the time.
Here is a guide on how to do it
Connect this via Ethernet to your main router. I used an Intel NUC with Pfsense on it for my router. But for my relatives I had Asus routers flashed with Merlin's custom firmware on them (you should be able to get Asus routers cheap used from CEX or Amazon's warehouse).
The VMG8924-B10A I got slightly faster speeds from it (talking like 3mb/s more speed), but its much bigger than the small sleek VMG1312-B10A so its a trade off over what is more important to you.
You can also go to Kitz forums and flash their custom firmware's onto them to get jumbo frames support etc.
I had this above setup also when I was with BT, Sky and Plusnet too. The Zyxels are amazing routers. I got much better speeds out of them than any other router/modem connected to my socket.