Yes, you can use Powerline Adapters or Broadband Extenders with BT TV.
If you have subscription channels, these are delivered over your broadband connection. Because of this, they work best when your box is connected directly to your Hub with an Ethernet cable or using Broadband Extenders.
Older Powerline Adapter products aren't supported.
You can buy Powerline Adapters at www.shop.bt.com >