Updated
The number on a speed-test website is not the number that matters. What matters is the speed that stays there for the whole programme, on the device that is playing it.
The figures we use
A steady 10 Mbps is enough for HD. 4K wants about 25 Mbps, and you want headroom if someone else is on a video call. Those are the figures in our setup guides. A line that bursts to 100 Mbps and then falls over will still buffer.
Test while the television device is the thing on the network, not only your phone. Wi-Fi on 2.4 GHz, through a wall, is a common reason a “fast” package still pauses. 5 GHz or a cable is the fix. A stick hidden behind the TV is in the worst spot in the room.
When to choose HD
Drop the player to FHD if 4K stalls and HD plays. You are not missing the subscription. You are matching the stream to the line. Many sources are not true 4K anyway. The label follows whatever the channel provides.
What a faster package will not fix
A wrong password, a MAC address that does not match, or an app that never received the playlist will not start, at any speed. Get one HD channel playing before you upgrade broadband. If Ethernet still fails on every channel, contact support with the device name. If only one channel fails, name that channel.
More on the symptoms is in the buffering article. The device list, including what is not supported, is on the compatible devices page.