Firstly I'd like to welcome you to the forums and say that I'm really sorry to hear that you are experiencing some picture distortion on all non-HD channels at the moment, I really do understand how irritating this must be.
I've run some tests on your set top box, and can see some issues with the signal levels, so would like to look into booking a technician to call out and investigate further for you. I'll send you a private message in order to get things moving with this. Please look to the top left of this page where you'll find a red envelope icon. Click on this and you'll see my message.