The stock answer... if you're rebooted your box, then pixellation on live TV is a classic symptom of signal issues.
Check by calling 0800 5610061 that there's no known area faults. If not... then you have an "unreported" fault that VM need to rectify. Either by a replacement box, or (more likely) an engineer visit.
Yes, as is standard practice you will need to call Virgin to report service faults.
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