We had issues in the N6 area, was cleared and we still have no connection. Helpdesk told us it would solve itself between now and 21st May so refunded us £13 (wow) . Our neighbour is have the same problem, and just text me to say it's apparently the box and Virgin need to send an engineer. Who do I believe?
I've run the diagnostic on the box and the Web for the last couple of days. Run it again and it's saying its turned off, but I'm on the box webconsole, so it's on.
The technician will usually require access to check everything is ok after adjusting power levels else, so I would not just assume that everything is now permanently fixed. Temperature etc can cause levels to change. If a faulty piece of equipment was changed that might mean the tech did not need to visit you.
To be on the safe side, enter 192.168.0.1 into your browser and click on router status (do not log in). Check you upstream and downstream logs and make sure the power levels are okay. See Sephiroth's guide under Broadband, Speed section of the forum or cut and paste the logs on here and one of the experts will advise.