Currently they're funded through the "TV charge" which is a nasty footnote to life in the UK. Regularly I get hatemail through the letterbox telling me what a bad person I am for not paying the fee (mandatory for all owners of televisions), presuming that I have a TV.
Yes, you can call them up and tell them that you're not a crimial, but that's not how life in a free country is meant to work, and I'm damned if I'm going to play the game. "Return to sender" every time.