Ah. Powerline adapters. I have a BT IPTV 4K-UHD streaming box ('YouView') which has ethernet and no wifi - presumably because at the time the BT Hub wifi was likely to be too slow. It came, unusually, with about 10m of ethernet cable. It warned that if the router was further away than that you could try powerline, but it would probably be too slow for UHD. I bored through a wall to get ethernet to it and laid flat ribbon ethernet under the carpets. I could probably have used a wifi bridge but that would have been expensive - two WAPs.