Extra channels are delivered over multicast, and your router may not support it. You will need to try the BT Home hub to see if that works.
If it does, then you need to look at you Netgear one to see if there are any options for multicast.
You should be able to get all of the FreeView channels, as they are delivered down your TV aerial. There are over 100 channels. If you are not getting them, check the signal level on the BT YouView box.
Is there any noise on your phone calls? Dial 17070 and select option 2, there should be no noise between the announcements.