Hi,
There are possibly 3 options. You should always have the router plugged into the master socket where possible.
Then you can either use a long ethernet cable. These are relatively cheap, abour £1 a metre from places such as amazon.
You can use home plugs (powerline adapters) to carry the network signal via your household wiring.
You can use wireless option, such as the TP Link WR702N Nano router to connect the TV box to the router.
Thanks
Karl.