Hi Rob
Welcome to BeoWorld.
First question, do you have an external box such as Sky or Virgin+ connected? If you have you will likely have a thin cable with an inra red emitter stuck to the front of the box and the other end plugged into the back of the TV.
It is possible that you have plugged the jack plug into the wrong socket, the sypmtoons would fit that. If you have the STBc emitter plugged in anywhere, remove it and see if the TV works. If it does, you just need to check the inside of the cable cover panel to see where the jack plug should be placed.
Hope that helps.
Regards
Opman