Oh they check!!
I advised them I didn't need a tv licence which at the time was true. I didn't watch iplayer. Did watch or record live tv. I informed them using email address X
I then wanted to watch something on iplayer as a one off, so made an account using my new email address Y. Watched about 2 programmes, that was it. (Technically I should have bought a licence at this point).
Totally forgot that logged onto a streaming stick at my friend's house, and they carried on watching iplayer for loads of stuff.
BBC have somehow tied the Y account to my address (no idea how) which is registered as no licence needed (X) and sent me an email to Y. I've obtained my data from them and my file was a very long list of exactly what programmes I've watched, on what device, and what date. (2 episodes of Luther at my house, and the entire box sets of 2 pints of Lager and a Packet of Crisps, and Gavin & Stacey watched by my mate.
I can't really argue I'm not the same person because my email addresses X and Y are basically my full name, and I'm also on the electoral roll for them to check. The letters in the post have got more and more threatening, with various deadlines for paying for a licence, dates when my details would be passed to the enforcement team, a date for when I'd be put on the list for a home visit, a date when they're do ABC, etc etc. I've heard they're just so busy this will never realistically happen and I've never got round to buying a licence or advising them I don't need one. They've now started sending letters to "The new occupier" instead of me directly.