You've not mentioned if this is C5-HD or C5-SD (confirmation of which might just give a few extra checks you can do), but the end result will likely be the same as what I'd hope the other customer you mentioned, was advised.
Call 0800 5610061 to check for any known faults in your area
If nothing's reported, call Virgin Media faults (150 from a VM phone, 0345 4541111 from any other phone) and report your fault. You will almost certainly need an engineer visit.
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