When I got one of these after getting rid of my TV back in 2003 or so, I used the link they provide to state that you have no TV (or maybe you had to call back then, I don't remember). The letters started again after three months so I just took to binning them.
I agree with this article that it's probably fake news [0]. It's also mostly moot now anyway, since if TV service is provided via Sky or Virgin, you're bang to rights. Same if you use BBC iPlayer, which is very good at detecting VPN use and so its very hard to hide your real IP address.
