If a TV Licensing inspector visits your home you are under no obligation to let them in. They can only enter your home with a warrant issued by a court. To get this warrant they need to prove to the court that they believe you are watching television illegally. Quite how they do this without actually entering your home is beyond me. If you are not watching TV illegally and an enforcer visits your home you are perfectly within your rights to say "goodbye" and close the door in their face.
They have scanners to see what is receiving the transmissions - however if you live in an apartment/flat with a shared roof-top aerial, then they can't prove anything.
At my old flat, me and my mates eventually bought one because of the annoyance it was causing - we had two people interrupt us, and about 10 letters saying a warrant was being issued.
Kind of shot myself in the foot there though because I bought my new TV and put my flat address for the TV licensing people at the till point. I should have put my parents address.
And apparently, the time it takes and the money it costs to issue a warrant just isn't worth it, for a silly TV license.
The BBC are all about "scare tactics" now. Fail a criminal record if you fail to buy one etc.
The Ryder Cup wasn't shown live on the BBC (only highlights), the World Cup Qualifiers (both Scotland and England) aren't shown on the BBC, and they have missed out on FA Cup coverage too I believe. Why? Because it costs so much to get those TV rights.
Yet they blow away all our money on paying Jonathan Ross £20m a year and other crap.
[/rant].