I don't watch TV either and I don't have license to. The quality of the BBC is just not worth the cost nowadays and I can't systand adverts every 10-15mins on other channels. Of course I have a TV but it's purely for my consoles/bluray/htpc. I do have a Netflix account and that's enough for me, it's cheaper and has a lot of BBC programmes not available on iPlayer ironically.
They harassed me a bit at first, kept turning up, telling me lies, and made a few threats of legal action but I turned it back on them and haven't seen or had any mail from them for ages. Just never sign anything and remember they have no legal right to enter your home, nor are you required to tell them the truth or prove your innocence.