I wouldn't let them through the door without a warrant anyway, and they would be wasting their time because we don't have a TV here!

They don't need a warrant -- like Customs and Excise, they have a statutory right of entry.

I didn't have a TV for years, and used to get letters (ranging all the way from very polite to very impolite) about once every four weeks. Once I tried ticking the "I don't have a TV" box and sending it back, but as all that did was increase the gap between letters to six weeks ("It's now time to update our records") I didn't bother again. One letter even alleged that an enforcement officer had visited but I was out.

Peter