If you don't let them into your house to see you have a TV, and you write them a letter saying you don't have a TV, and you withdrawal their (I believe its called) 'assumed right of access' and you say you will request any further communication to cease, and any more letters you will take them to court over harrassment, I'm pretty sure they leave you alone... they have never had a successful prosecution using 'detector van' evidence alone, its always been their 'enforcement officers' seeing a TV in the window, or you letting them and them seeing a working TV in the house...
might I also add, that if you only use a TV for DVD's and game consoles, de-tune your telly from all channels, manually tune each one to a frequency that doesn't receive any sound or picture, and tell them this, let them in to check the signals on each of the channels... make sure there's no antenna cable in the back...
If they go through and search for a signal, or ask for you to plug the telly into an antenna, they are modifying the current installation and are therefore 'installing' equipment, enabling you to get TV.
If you look carefully at the small print, the license fee is only required if you watch or record 'live' tv.... so if you can somehow delay the signal by 20 seconds, you wouldn't need to pay a license fee, nor would you need one if your TV was hooked up to a computer, and was used only for the BBC iPlayer, which shows recorded shows, not TV as its broadcast live.
I didn't pay my license fee for 3 years when I lived in my previous flat, as I never watched live TV, and used my telly for games, DVD's, and had it hooked up to the PC. And I had the telly licensing people in twice a year to check my channels, I eventually found out how to keep them away.
Tell them you don't need one (they will want to check this but they don't have to. Why ask a question you aren't going to believe the answer to anyway?)
Tell them they aren't welcome on your property.
Tell them they are harassing you by sending further letters.
Also something I said that might have helped, tell them that you have cctv
of your property, and their 'officers' visiting your house will have their pictures taken and posted all over the internet on anti-tv license websites.
I haven't heard from them in 6 months.
Alternatively, you can log into their website, and update your details... tell them you are moving overseas.... this will get your name off their register, which they will then send letters to 'the current occupier'.... which you can just ignore, they can't convict someone if they don't have a name. (you must remove your name from the public register with the council tax people if you want to go down this route...
Happy dodging. (not dogging... lmao)