Recently bought a fire stick for my room but the streams are constantly buffering, yet on my phone they are fine and in other rooms I can watch for a long time without any sort of interruption.
Is this due to the WiFi reception on the fire stick? If so, would it be worth investing in the Ethernet adapter so I can have a wired connection into my stick?
The wifi module in your phone is likely a lot better than the one in the firestick. An ethernet adapter gives you a fighting chance but a VPN will still slow you down a bit.
Try different servers on the VPN and run speed tests with your iptv off (don't keep testing the service on different servers as some providers have a limit on the amount of I.P's allowed within a 24hr period and some even have a time limit between I.P changes)