I had a similar problem a few weeks back with bad pixelation across all channels, I rang CS and we went through the usual stuff of re-booting my V+ and to my amazement the lady on the phone managed to sort out the problem.
She told me the power levels on my stb were low and that she had adjusted them, I too thought this could only be done by an engineer at the green box but obviously not, she sorted out an unwatchable tv signal back to excellent HD in about ten minuets...great service indeed.
