Welcome to the forum. You won't be able to use your Home Hub as the router for your NOW TV broadband. If you wanted you could connect the Home Hub to your NOW TV Hub and use it as a switch for extra Ethernet ports (you'd probably need to turn DHCP off on the BT Home Hub and turn wifi off to avoid conflicts, although make sure you have a device such as a laptop/PC that you can connect via Ethernet to administer the Home Hub before you do this).
NOW TV don't use PPPoA authentication on their routers so I'm afraid you would need to use Sky/NOW TV routers to connect (I'm afraid any discussion of how to get around this wouldn't be allowed on this forum). So if you are needing additional Ethernet ports you'd need to connect a dedicated switch or something similar.
There's a blog here on how to use a Home Hub 5 as a switch if you wanted to give this a try - instructions for HH5 but guess it would be roughly similar for other models.
A SkyQ Hub will work with no problems with NowTV Fibre Broadband.
It would also appear that NowTV are now supplying a rebadged version of it to new customers.
Sorry just re-read your initial post and one of the 'moans' was more ethernet ports, so you've probably already been supplied with a SkyQ Hub clone.
Hi @Anonymous User
Have a look at Ethernet Gigabit switches from Amazon or Ebay for around £15 for an 8 port Hub.
i have a Trendnet 8 port switch in my home network setup connected to my Router it was simple to setup (plug and play) and never had any issues with my internet connected devices over Ethernet