Ive managed to sideload the bt sport app onto firestick. Got it working but the stream is all choppy and lagging. The same stream is fine through my tablet. Ive tried changing the display resolution on the firestick that hasnt helped. Any ideas how to fix this?

It could be the bt app itself its not great here on my fire tv 2015 either

How do I side load - I have fire tv box gen 1

Download a free program called adbfire to your PC, you can then push various files like Zip & APK to your Fire device. You will also need the fire launcher as well, this doesn't jailbreak your device at all, it just adds a side launcher in which you can install apps not approved by Amazon, like the marvellous Kodi.

You also have to go to System on the Fire Stick and turn on developer options and debugging, without this no unofficial apps can be sideloaded with ADBfire.

BT Sport has stopped on my Amazon Fire TV box.

Get an error message VN009 (your operating system is no longer supported) and then a message to upgrade to latest version of the app.

Latest version (2.11.0) won't sideload as it needs the new Android 5.1 software version that hasn't arrived at my box yet (due this month).

It's working fine (so I'm told) with the gen 2 Fire TV boxes that have 5.1.