That's partly my point, there could now be a question mark on your status however in your case they still have records due to you paying tax. i failed to fill in the electoral list a couple of times and then people came round my house in person to check.
It's not like the 70's and 80's, now, everything is pretty much linked and on a central database that all agencies seem to has access to.
My friend used to claim reduced council tax, 2 weeks after his friend moved in he got a letter stating he was no longer entitled to it,