PSN has been failing to connect more often than not ever since I put GTA V to download (using TCG's download method) and later installed it before I began playing the game. Often when I test connection, PSN fails or even if it does succeed, NAT fails. I am still able to sign in at times but I wouldn't be allowed inside the The Last of Us lobby because there would be no information on NAT because it would have failed. There are few times when connection test passes but that's seldom these days.
You know what all this is about? Are UK subscribers facing any such issues?