As an addendum to this thread, the people who may or may not knock at the door have no right to enter the property unless you invite them in.
They have NOT got court orders/ warrants or any of the other crap they claim to have to force entry, no court in the UK will give them a court order to do this and I challenge anyone to find an instance of this via google or the search engine of your choice - it's never happened and never will.
The only time someone gets dusted for not having a TV licence is when they knock at the door, you invite them in to check, and when you admit to not having a licence, even then, 99 times from a hundred, they make you buy a licence using a debit/credit card, if they do this, cancel the payment ASAP.
Bear these points in mind:
1) they have no idea who you are or what your name is - you could have moved in this morning
2) They have no right to come in the house, tell them to come back next month
3) if someone knocks at the door and say they are from TV licencing just close it and go and watch TV, I've had 3 people in 10 years