To be perfectly frank these web based speedtests are not that accurate. A better test would be to download a file from Virgins ftp site and look at the download speed.
I am on virgins 20mb bb and I get (outside of the throttling time
) speeds up to 1.2mb/s. Which seems fine.
It would be worth also considering if your router is configured correctly if you use one and if the contention ratio in your area is high.
All the best