Hi
I have had exactly the same issues with moderate to very bad picture breakup . This has been going on for the last 3 to 4weeks ironically coinciding with virus lockdown. I have re booted the box, checked all connections (tightening with a spanner to make sure) and even changed the HD cables as suggested on the virgin media website. This does sometimes work for a short period then the pixellations return!!
I have also made sure that the box has been well ventilated (noting this from a previous post) but this does not make any difference either.
Can someone please get back to me with some remedy to this very annoying problem - I am paying for a service that has clearly not been working properly for too long.