You need a 4k TV that has been approved to run BBC Iplayer in UHD mode (not all of them have), however, I have one of those, so I'm all set to go yes?, well it turns out you need something else I don't have, a 10 Mbs broadband connection, my 4-5 Mbps causes the BBC Iplayer UHD mode to throttle back to something that looks more like 720, so if anyone knows of a download link for the 4k files I would be very interested
My LG OLED loves it and the images are quite wonderful. I do however have 50mbs so I do get the full bandwidth. I understand that the BBC server negotiates a bandwidth with your IP address and supplies that. They do recommend 40mbs for best picture. I enjoy "how we did it" at the end almost as much as the programme.