My dad has bttv, and I setup high power Powerline adapters from the router upstairs to the TV downstairs. It is said that the BT TV requires a BT Powerline adapter, so I use a TP link 8020 as the main which is a gigabit pl adapter and the second is under my work station desk for working on laptops/pc's, I then use a BT flex 1000 by the TV downstairs and there are never any issues.. I've used the BT TV app in the box to run speed checks and it says it will run every viewing quality fine with all green ticks and then I can use the Netflix app to do a proper speed test from the box too and that always returns a good speed usually around the max we get minus a small amount of loss.
Now, I fully appreciate that lots of people don't rate PL adapters, but I'm far too OCD haha 😉 to stop there..
I've made sure the tplink ones have the latest firmware, and you can either use their software for a pc to add BT ones using the code on the back or use the pairing buttons.. I always use cat6a cables and not the bundled ones as there pants!!
This then, shows up in the router manager as a gigabit connection and not a 100mbps connection..
With the proper research and sadly expenditure, good results can sometimes come...
It's trial and error, but if we make sure that our end is solid then any other issues can't be our fault, within reason..
If you have the money to spend on good quality pl adapters then you can, at least in my experience, create a good network.
If you buy the throughput adapters then you don't lose a socket.
On Amazon, duronics cat6a triple shielded ethernet cables are very reasonable in price..