Non of the cars you have mentioned have your address registered to them otherwise DVLA would have been sending you reminders every year for either tax or Sorn, and then an automatic fine for not doing either.

If you've had no letters they don't know where you live.
But the first time you try and tax them or register the correct address expect a big bill and fine.
Unless you are talking about MODEL cars,

Sorn is yearly not 6 monthly and it's so widely publicised and talked about on Forums you must have been living out of the country to have missed it

.