How are you accessing Iplayer/Netflicks ?, on a smart TV, tablet , phone, ?
Is your router (home hub) plugged into the master phone socket or an extension socket ?, is anything connected with an Ethernet cable or is everything WiFi connected ?
First thing to do is (if not already done) connect the Home hub into the master socket test port, and connect a device (laptop/pc/smart Tv) with an Ethernet cable and try a to watch something on that wired device to see if any improvement.
Other things to try , plug a known working phone (preferably a corded phone) into the test socket , dial 17070 , take the 'quiet line test' option, and listen for any noise...if the line is noisy , report it to your landline provider .
Access your router advanced settings page and post the report , TBH, Netflicks and BBC I player should work OK with quite modest speeds (2-3Mb) , when you try and use these services, are others using your broadband at the same time ?