Hi , I`m JackPerhaps I can help you with this problem , a few questions coming up and please note that it may take a few minutes between replies;
Was that talktalk remote programmed and working with this tv prior to this ?
Actually it looks like the tv may be the culprit here if both remotes failed to operate it at the same time.
May still be a good idea to test the TV's own remote before calling the bloke though.
Do you happen to have a cell phone camera , a tablet , a digital camera etc. , any camera that has a display or screen to test the remote ?
If so then here is how to test your remote;Turn on the camera and point the front of the remote at the camera lens ,then while looking at the remote through the screen press buttons on the remote.If the remote is working, you should see light coming out the front of it while looking at it through the camera screen.If you see nothing coming out and are not sure if you did the test correctly then try it with a known working remote.
If you cannot test it at home then any repair shop will test it for you free of charge and if it turns out the remote is the culprit then you can get a new one at the link below , just click on it ;
If the remote is fine then this would point to a defective remote sensor in the tv .
Those are not very expensive and usually cost around 10 pounds to buy but you may need that tv repair bloke to replace it .
Perhaps 80 pounds where you are call different shops with the info you have now , it pays to shop around.
Let me know if you have other questions and if not for now then please do not forget to rate by clicking on the star icons at the top, then click on Submit so i get paid for my time helping you .Also note that the rating does not close this post , you can come back at any time if you have questions or need help at a later time . Thank you