Macbook Air problems with Virgin Media Super Hub

Any time I am at home and try to use the internet, it is so slow a connection that it is practically useless.

My computer has no problem with any other networks, I always get great connection at work or in cafes, or pretty much anyone elses house. It's just my own bloody house that is the problem. I also can't simply change providers, as it is my housemates' wifi and I am only renting for 1 year. But I am still paying for it, and right now I am paying a lot of money for essentially a non-service.

I have used diagnostics, and assistant. Renewed DHCP, and even gone for the whole public DNS thing, and nothing works. I can't send emails, watch iplayer, or even listen to radio. But the whole time this is happening the Airport thinks it has a great connection, which makes it impossible for diagnostics to detect anything out of the ordinary. I

have spoken to virgin who have installed both a new hub and new wires, but with no change. I have also been on the phone to Apple themselves, who suggested the public DNS, which worked, until I took my laptop to work after the weekend. When I got back from work, having had the computer linked up to my work's wifi network that day, my computer was back to the same problem, even with the public DNS in use.

The whole situation is absolute pants! And I am at the end of my tether. Please could someone provide some insight?