Well, it's currently a free service for Britons. (I guess they assume you all pay your TV license.) They probably don't have a good way to charge people.
No, as previously stated it's most defiantly not free, the current cost for one house hold is £142.50. And they have a great way of collecting that, it's called the law. They assume that every house in the UK has a TV of some form and if you don't register a TV licence they will start sending you letters and eventually the threat is followed through with a man knocking on your door. They used "TV Detector Vans" at one point but I think it was largely accepted that was just a scare tactic, now they use the power of the government database. As stupid as it sounds they have a very low tolerance for people not paying and people do go to jail if they refuse to pay and the fines can be quite substantial too.
Cheers
Cris.