Back on topic
If you look at the detail of the Press Release that VirginMedia made you'll see that they were saying some tests are not as good as others. If Virgin kept their testing environment consistent then this is pretty good insight. Reference this graph;
where you can see several sites (not named) were close at the top, and the rest ranged from not so good to downright bad.
The slide also referes to headline speed so perhaps these results were 20Meg rather than 50Meg?
The whole article is at
Hexus.channel
The article also mentions monthly testing so maybe we will see some more in the next couple of weeks.
I'd guess
www.thinkbroadband may be predicting some good results so have got their piece in early if they are confident!