We have always been aware that there is a mobile telephone mast in the woods above the property. I realised it was more than a mobile phone mast when I saw the deeds providing access to the mast on behalf of the IBA.
We walked up into the woods today and had a closer look. A quick search online proves that it is indeed a television transmitter as well as a mobile phone mast. More details here: http://www.ukfree.tv/shutdowndetail.php?tx=SE148105
The mast is a few hundred meters from the property and is largely obscured by the woods (certainly in summer with leaves on the trees).
And I guess the other thing is that by the looks of the map above, we should get great reception of digitial TV. Strangely I have looked through all the photos of the property that we have taken and none of them have got the mast in shot.